The Forgotten History of Aquaponics

Abstract

This paper re-examines the Integrated Aqua-Vegeculture System (IAVS), a pioneering and highly efficient approach to sustainable food production developed in the 1980s. IAVS predates the popular term “aquaponics” and has been mistakenly conflated with less efficient systems due to modifications and the spread of misinformation online. This paper clarifies the distinct features of IAVS, emphasizing its unique use of sand as a biofilter and growing medium, contrasting it with gravel-based systems that have become prevalent in modern aquaponics. The paper analyzes the historical factors that led to the overshadowing of IAVS, including the Speraneos’ modifications and the rise of inaccurate terminology like “Sandponics.” It argues for the importance of proper nomenclature and a return to the scientific rigor that underpinned IAVS’s development, highlighting its potential to address current challenges in sustainable food production. By revisiting the principles and research behind IAVS, this paper seeks to re-establish its significance and offer valuable insights for researchers and practitioners seeking to advance the field of aquaponics towards a more sustainable and productive future.

Introduction

Global food demands are expected to double by 2050 (Tilman et al., 2012); this is driven by the growing human population and the increased need for animal feed (Gan 2013). This demand presents significant challenges, especially in arid and semiarid regions where water scarcity limits agricultural productivity. The search for sustainable food production methods has led to the development of innovative systems like Integrated Aqua-Vegeculture System (IAVS). IAVS, pioneered by Dr. Mark McMurtry in the mid-1980s, offers a solution by integrating fish farming and vegetable cultivation in a closed-loop system.

While IAVS predates the popular term “aquaponics,” it has been mistakenly referred to as “Sandponics” due to social media trends and a lack of thorough literature reviews. This confusion, coupled with modifications introduced by others and the rapid spread of information online, has led to a situation where IAVS, a scientifically validated and highly efficient system, has been overshadowed by less efficient aquaponics systems.

This paper aims to shed light on the origins, principles, and benefits of IAVS, contrasting it with other systems and highlighting its potential to address current challenges in sustainable food production. By revisiting the principles and research behind IAVS, this paper seeks to re-establish its significance as a pioneering and highly effective approach to sustainable food production, offering valuable insights for both researchers and practitioners in the field of aquaponics.

Historical Context and the Origins of Aquaponics

In arid and semiarid areas, scarce and unpredictable precipitation and low water availability are the major factors limiting agricultural productivity (Gan et al., 2009; Siddique et al., 2001; Turner, 2004a); this issue has become more serious as global climate change has significant impacts on agricultural systems (Chmielewski et al., 2004; Turner and Meyer, 2011). Inefficient use of scarce water, coupled with drought and heat stress during the cropping season, threatens agricultural sustainability in dryland environments (Siddique et al., 2012; Turner, 2004b).

In the late 1960s and early 1970s, the idea of ‘Limits to Growth’ became an important topic of discussion around the world. This was largely because many issues were happening at the same time, including problems with food production, population growth, city development, environmental damage, energy shortages, and the depletion of natural resources. During this time, many experiments were started to find new, sustainable ways of producing and consuming things. These efforts were driven by community groups, as well as leaders from businesses and universities. (Kledal 2018).

Aquaponics originated from the realm of aquaculture, as aquafarmers investigated techniques for cultivating fish while simultaneously seeking to minimize their reliance on terrestrial resources, water, and other essential inputs. The concept of aquaponics is frequently linked to the extensive research conducted by the New Alchemy Institute, established by John and Nancy Todd, along with William McLarney in 1969, and the contributions of Dr. Mark McMurtry at North Carolina State University. (Bradley 2014; Kledal 2018).

The Emergence of IAVS and Early Aquaponics Research

The term, “aquaponics,” begins to appear in the titles for academic literature in the late

1990’s. Prior to this, the literature reveals that what would today be termed as

aquaponics was referred to in the 1970’s and 1980’s by names such as “hydroponic aquaculture pond,” “hydroponic solar pond,” “integrated agriculture,” “integrated aquaculture,” “integrated fish culture hydroponic vegetable production system,” and “Integrated Aqua-Vegeculture System (IAVS) (Goodman 2011).

Aquaponics, as we know it today, has its roots in the early 1980s to early 1990s, with Mark McMurtry being acknowledged as its originator. McMurtry and Professor Doug Sanders developed the Integrated AquaVegeculture System (IAVS) at North Carolina State University, which involved water flowing through a bed of medium-coarse sand (McMurtry, et al., 1990; McMurtry, 1992). Concurrently, the New Alchemy Institute was also developing aquaponics, as reported by Zweig (1986). The IAVS and the deep-water-culture system (DWC) have become the two dominant systems in modern aquaponics (Marklin 2013). Tom and Paula Speraneo later adapted the McMurtry System, introducing the term “flood-and-drain system,” which is now favored by backyard practitioners. However, IAVS proponents have strongly criticized this adaptation (Konig 2018; Rharrhour 2022; Milliken 2021).

IAVS is a sustainable method of food production that integrates the raising of fish (aquaculture) with the cultivation of fruit and vegetables (horticulture), highlighting the unique use of sand as a key component. IAVS operates as a closed-loop, recirculating system, minimizing water usage and waste discharge (McMurtry 1990a). The system is designed to be low-tech and easy to maintain, with minimal water exchange needed (averaging 2.8% daily).

The IAVS research and findings confirmed much of the background science that underpins aquaponics, the research at North Carolina State University was discontinued because it was ready for commercial application and usage (McMurtry 1997b; Bradley 2014; Mandal 2023; Goodman 2011).

IAVS: A Pioneering System Predating Modern Aquaponics

IAVS predates the common use of the term “aquaponics”. While IAVS shares some similarities with modern aquaponics, it represents a distinct and pioneering approach with unique characteristics that set it apart. A crucial distinction lies in the integration of horticulture in IAVS, rather than the hydroponics commonly associated with aquaponics.

USDA

From 1992 to 1993, a USDA grant of $100,000 funded a commercial demonstration project in North Carolina led by Boone Mora and Tim Garrett. This grant covered greenhouse construction and operating expenses for one year. Despite minimal external assistance—aside from a three-day workshop by McMurtry—the project exceeded expectations despite challenges such as suboptimal management practices and pathogen introduction due to frequent visitors.

Produce from this project was sold locally at discounted prices to cover labor and distribution costs. However, there was uncertainty about what became of approximately 22,700 kg of tilapia produced during this period since tilapia was not well-known in rural North Carolina at that time. Ultimately, the greenhouse was sold to another farmer for tobacco production per grant terms, with proceeds returned to the USDA.

Dr. McMurtry was unaware of this trial until its publication in Furrow magazine, and subsequent attempts to confirm the trial’s details with the USDA have remained inconclusive.

FAO

On July 17, 1989, the NCSU iAVs Research Group contacted Dr. Khadi of the FAO Irrigation Program in Rome to share detailed information about iAVs technology and its potential applications in regions facing food and water shortages. This outreach was encouraged by both USAID and USDA/OICD. Despite these efforts, no response was received.

Dr. Douglas C. Sanders, Chair of the iAVs Research Group, visited the FAO headquarters in Rome on September 2-3, 1990, where he believed his presentation was well-received. However, despite multiple follow-up attempts, no further communication was received from FAO officials.

Namibia

In early 1990, as Namibia transitioned into a newly established republic, Dr. Mark McMurtry secured the support of U.S. Senator George Mitchell, then Senate Majority Leader, and Robert C. Byrd, Chair of the Senate Foreign Appropriations Committee. Collaborating with Sir David Godfrey and the Rössing Foundation, their collective goal was to implement iAVs across Namibia. This initiative aimed to address food security challenges and promote sustainable agriculture in the region.

Namibia’s first President, Dr. Sam Nujoma, personally expressed gratitude to North Carolina State University (NCSU) for Dr. McMurtry’s contributions to improving food security in the country. By March 1991, a comprehensive five-year development plan was formulated to advance this initiative. A special appropriation of US$7.5 million (equivalent to approximately $18 million today) was secured through Senator Mitchell’s efforts to fund integrated agricultural projects throughout Namibia.

The proposed implementation of IAVS in Namibia with USAID funding of US$7.5 million further strengthened NCSU’s confidence in the technology’s scalability and potential impact. The Namibia project was abruptly halted due to the misappropriation of the allocated funds by a USAID Mission Director, , who redirected them toward housing projects intended to attract staff to Windhoek. Despite objections from the U.S. State Department, Congress, and the Administration regarding this diversion of resources, the funds had already been expended and could not be recovered.

This incident dealt a major blow to IAVS’s momentum and undermined NCSU’s efforts to showcase its real-world applicability.

Dr. McMurtry actively fought against NCSU’s attempts to license IAVS to multinational agricultural corporations, believing that the technology should remain open-source and accessible to all, particularly those in developing countries. This stance created friction with university administrators who saw commercial potential in IAVS. While Dr. McMurtry was focused on international outreach and battling NCSU’s commercialization attempts, Tom and Paula Speraneo’s modified, gravel-based system, which they branded as “Bioponics,” began gaining traction. They actively promoted it through early online channels, capitalizing on the emerging internet’s reach. As the Speraneos’ gravel-based system, often mislabeled as “flood and drain aquaponics,” proliferated, awareness of the original IAVS waned. The term “aquaponics,” which became popular in the late 1990s, further contributed to the confusion surrounding the distinct characteristics and benefits of IAVS. The combination of these factors led to IAVS becoming relatively obscure, while less efficient systems gained popularity. This situation highlights the challenges of disseminating open-source innovations and preserving their integrity in the face of misinterpretations, commercial interests, and the rapid evolution of information channels like the internet.

Richard Diver identifies the North Carolina State University system as the next to be developed and as the locus for one of the two main branches of aquaponics. Although McMurtry’s scholarly work reviewed does not discuss profitability, he does have one magazine article discussing the economics of aquaponics, which he co-authored with Doug Sanders in 1998, titled, “Fish Increase Greenhouse Profits,” in The American Vegetable Grower.36 As a rationale for the conclusion that integrating aquaculture into hydroponic systems can increase profits, this article with three pages of text asserts, “The system provides economical yields of vegetables and fish. The fish system is profitable on its own and when the vegetable component is added profits are further increased.” (Goodman 2011).

Tom and Paula Speraneo

In December 1989, Dr. Mark McMurtry hosted a three-day workshop at the Meadowcreek Project in Fox, Arkansas, which was attended by faculty, students, aquaculture professionals, and Tom and Paula Speraneo, owners and operators of S & S AquaFarm in Missouri. They wanted to build their own IAVS, however, they couldn’t afford the sand crucial to IAVS and decided to use gravel from their driveway instead.

The use of gravel created many issues and complications, and they were counseled at length by Dr. McMurtry not to modify the IAVS design. He strongly emphasized that gravel would not provide the same level of mechanical filtration or support the necessary biological activity.

By using gravel, the plants would dry out and so they had to use continuous pumping and install a bell syphon, both of which led to more complications and more costs. By using gravel instead of sand, it removed the filtration capacity and so the Speraneo system only works well if the system is fitted with dedicated mechanical and biological filtration. If not, the system will bear the risk of an eventual ‘collapse’, due to the accumulation of organic matter using up oxygen in the system needed for the fish and furthermore reduced aeration of media bacteria and the plant root zone (Kledal 2018).

The Speraneos took what was an open source concept and chose to make it private so that they could sell, and profit from, their instructional kits. The Speraneos created a resource manual and were actively involved in disseminating information about their aquaponics system, welcoming 10,000 visitors onto their farm. The Speraneos’ system was deployed widely in schools and in many commercial aquaponics operations.

The Freshwater Institute in Shepherdstown, West Virginia also created a further iteration of IAVS known as the Tallmansville system. In 1998, the Freshwater Institute produced several manuals on aquaponics production. A survey of the institute’s manuals reveals that, with one notable exception, most of these publications focused on how to design and operate aquaponics systems (Goodman 2011; Bogash 1997).

The story of the Speraneos and the Freshwater Institute and their impact on IAVS is a tale of unintended consequences and the challenges of maintaining the integrity of an open-source innovation.

The Speraneos’ decision to use gravel had several negative consequences for the development and popular understanding of IAVS:

Reduced Efficiency: The gravel-based system is significantly less efficient than IAVS in terms of water filtration and nutrient cycling. Gravel’s larger particle size limits mechanical filtration, reduces beneficial soil organism populations, hinders aeration, and ultimately leads to lower fish and plant yields. This decreased efficiency undermines the core principles of sustainability and productivity. Gravel, with its larger particle size, cannot effectively trap fine solid waste particles. Sand’s finer grain size, on the other hand, provides superior mechanical filtration, preventing these particles from returning to the fish tank and causing water quality issues. The Speraneos’ gravel-based system struggled to maintain clean water, which is essential for fish health and overall system stability.
Misrepresentation of IAVS: The Speraneos’ modified system, widely disseminated as “flood and drain aquaponics,” overshadowed the original IAVS. This misrepresentation led to a misconception of IAVS as a less effective system. Many people adopted the less efficient “flood and drain”. method, unaware of the significant difference in performance compared to the sand-based IAVS.
Commercialization and Distortion: The Speraneos’ decision to commercialize their gravel-based system further contributed to the distortion of IAVS. They developed information packages and sold them, capitalizing on a modified version of Dr. McMurtry’s open-source innovation. This commercialization contradicted Dr. McMurtry’s vision for IAVS as a freely accessible solution for food security, particularly for those in need.
Clogging: Paradoxically, while gravel might seem less likely to clog than sand, the reduced biological activity and aeration it provides can actually lead to a buildup of organic matter, creating conditions ripe for clogging. Sand’s superior filtration and aeration capabilities help prevent this buildup, ensuring a smoother flow of water and nutrients throughout the system.

The Speraneos’ actions ultimately hampered the widespread adoption of the more efficient and sustainable IAVS. Their modified system, while simpler, propagated a less effective method and created confusion about the true potential of IAVS. Dr. McMurtry has expressed deep regret over these developments, emphasizing that the Speraneos’ gravel-based system represents a significant deviation from his original vision and intentions for IAVS.

The Speraneos’ switch from sand to gravel in their aquaponics system led to a cascade of issues, ultimately forcing them to abandon the intermittent irrigation technique central to IAVS and implement continuous pumping with a bell siphon.

Here’s a breakdown of how this unfolded:

Gravel’s Deficiency: As discussed, gravel’s larger particle size makes it less effective at retaining moisture compared to sand. The sources repeatedly emphasize that the sand in IAVS is crucial for maintaining a moist environment for plant roots. When the Speraneos substituted gravel, the plants likely experienced drying out, especially in the upper portions of the grow beds that were not constantly submerged.
Shift to Continuous Pumping: Faced with drying plants, the Speraneos had to abandon IAVS’s intermittent irrigation technique, which involved timed cycles of flooding and draining the grow beds. They resorted to running the water pump continuously to ensure the gravel remained saturated and the plants received sufficient moisture.
Root Drowning and Rot: Continuous pumping, while addressing the drying issue, created a new problem: root drowning. Constantly submerged roots are deprived of oxygen, leading to root rot and plant health issues. This is precisely why Dr. McMurtry developed the intermittent irrigation technique in the first place—to prevent root drowning and ensure proper aeration.
Incorporation of the Bell Siphon: To mitigate root drowning caused by continuous pumping, the Speraneos incorporated a bell siphon into their system. This device automatically drains the grow bed once the water level reaches a certain point, allowing for periods of air exposure for the roots. However, adding a bell siphon introduced more complexity, potential points of failure, and additional costs to the system.

The Speraneos’ modifications highlight a crucial point: deviating from the carefully designed principles of IAVS, even with a seemingly simple substitution, can trigger a domino effect of problems. Their gravel-based system, while promoted as “Bioponics” and gaining popularity due to its simplicity, ultimately became a less efficient and more complicated approach compared to the original IAVS. The need for continuous pumping increased energy consumption, while the bell siphon added complexity and cost. These unintended consequences underscore the importance of adhering to the scientifically validated principles of IAVS for achieving optimal results in aquaponics.

The Importance of Sand as a Biofilter

The use of gravel instead of sand in an aquaponics system would significantly alter the microbial community, both in terms of variety and quantity. The use of soil microbes is a significant advantage of IAVS, and this advantage is directly tied to the use of sand as the growing medium.

Surface Area: Sand, with its much finer particle size, offers a vastly greater surface area for microbial colonization compared to gravel. This means more space for a wider diversity of beneficial bacteria, fungi, and other microorganisms to establish and thrive.
Moisture Retention: Sand’s ability to retain moisture creates a more favorable habitat for microbes. A moist environment allows for better nutrient diffusion and supports a wider range of microbial metabolic activities. Gravel’s poor moisture retention creates drier conditions that restrict microbial growth and diversity.
Aeration: The intermittent irrigation technique, central to IAVS, ensures cycles of flooding and draining, providing essential oxygen to the microbes in the sand bed. Oxygen is crucial for the aerobic bacteria that drive nitrification, the process of converting harmful ammonia from fish waste into plant-available nitrates. Gravel, even with a bell siphon, cannot replicate the thorough aeration achieved by sand with intermittent irrigation.
Organic Matter Accumulation: Sand’s superior filtration capacity helps prevent the buildup of excessive organic matter, which can create anaerobic conditions that are detrimental to beneficial microbes. Gravel’s larger spaces allow more organic matter to accumulate, potentially leading to an imbalance in the microbial community.

The rich and diverse microbial community fostered by sand in IAVS is a key advantage of the system. These microbes play vital roles in:

Nutrient Cycling: They break down organic matter from fish waste, releasing nutrients in forms that plants can readily absorb. This natural process eliminates the need for external fertilizers.
Disease Suppression: Beneficial microbes can outcompete and suppress harmful pathogens, protecting plants from disease.
Plant Growth Promotion: Some microbes produce hormones and other substances that directly stimulate plant growth.

Science is based on observable and measurable things/phenomena. However, there is no absolute scientific truth; it is just that some knowledge is less likely to be wrong than others (Nayak & Singh 2015).

Statements produced through scientific research must be testable, and research by itself must be reproducible (a good scientific paper is one which enables the method to be replicated). Research is termed ‘scientific research’ if it contributes to the pool of science and follows the scientific method.The field of aquaponics is quite new, with the first scientific paper specifically using the term appearing in an impact journal in 2004 . Many advancements had been made before that, namely by James Rakocy and his group (University of the Virgin Islands) but their publications are more demonstrative and less experimental. According to the Web of Science, more than 60 peer-reviewed papers have been published on aquaponics since 2004, but many articles concentrate more on promoting the potential of aquaponics than on completing scientific trials per se. Part of the problem stems from having enough replicates and establishing proper control groups. When looking at the literature, we normally see very few or no replicates, or two replicates per treatment at the most. (Milliken 2022).

Scientific Rigor in Aquaponics: Contrasting IAVS with Other Approaches

Additionally, as with a majority of Rakocy’s research, the productivity numbers in this study are based on an outdoor tropical growing system where warm weather and many hours of strong sunlight translate into productivity levels for tilapia and vegetables that tend to be higher than in more temperate climates. Furthermore, in cold climates an outdoor field system would not be feasible year-round. Consequently, Rakocy’s conclusions are not directly applicable to aquaponics systems in more temperate climates. (Goodman 2011).

The story of James Rakocy and his work in aquaponics highlights a concerning trend in the field: the presentation of experimental demonstrations as rigorous scientific research. While Rakocy has undoubtedly contributed to the development of aquaponics, much of his work lacks the necessary scientific rigor to be considered true scientific research.

Here’s a breakdown of the key points:

Early Adoption of DWC: Rakocy is often credited with pioneering the Deep Water Culture (DWC) or “raft” system in aquaponics. The concept of DWC originated with Ron Zweig and Bill McLarney at the New Alchemy Institute in the mid-1980s, predating Rakocy’s work. This fact is often overlooked, leading to the misattribution of DWC’s origins. McMurtry co-presented a seminar on integrated aquaculture with Ron Zweig at the Woods Hole Oceanographic Institute in 1989.
Demonstrations vs. Scientific Research: A key criticism leveled against Rakocy is that much of his work at the University of the Virgin Islands (UVI) was presented as research but, in reality, it consisted mainly of demonstrations. Demonstrations showcase the feasibility of a concept, while scientific research involves controlled experiments with replications and statistical analysis to draw valid conclusions. The sources suggest that Rakocy’s work lacked the necessary replication and statistical rigor to be considered true scientific research.
Lack of Financial Data: Another criticism is the lack of comprehensive financial data in Rakocy’s publications. While he has published some data on productivity and gross income, he often omits crucial information about capital costs, operating expenses, and marketing costs. Without this information, it’s impossible to determine the true profitability of the systems he promotes, which is vital for farmers, investors, and anyone considering commercial aquaponics.
Misrepresentation of Rainfall Levels: Dr. McMurtry has stated that Rakocy misrepresented rainfall levels at his UVI research facility, leading to inflated claims about water efficiency. Dr. McMurtry alleges that Rakocy didn’t account for significant rainfall, which artificially reduced the apparent water usage of his systems.

These points raise concerns about the validity and applicability of some of Rakocy’s findings. Presenting demonstrations as research without proper scientific methodology and omitting critical financial data can mislead those interested in aquaponics and hinder the development of the field as a rigorous and credible scientific discipline.

IAVS stands out from other systems because of its rigorous adherence to the scientific method, a key factor in its validation and effectiveness. Here’s how iAVs was built using scientific principles:

Hypothesis and Experimentation: Dr. McMurtry’s initial hypothesis was that integrating aquaculture and horticulture in a closed-loop system, using sand as a biofilter and growing medium, could create a sustainable and efficient food production method. To test this hypothesis, he designed and built experimental iAVs systems at North Carolina State University (NCSU).
Replicates and Controls: A hallmark of scientific research is the use of replicates and controls to ensure the validity of the results. Dr. McMurtry’s dissertation research involved constructing an iAVs system with 16 tanks, allowing for testing of four different tank-to-filter volume ratios under various conditions. These ratios were tested across three crop intervals and included a non-crop period. This approach allowed for a thorough assessment of the system’s performance under varying conditions and provided statistically significant data.
Data Collection and Analysis: Throughout the experimentation process, meticulous data was collected on key parameters, including:

Water quality: Ammonia, nitrite, nitrate, pH, dissolved oxygen levels.
Plant growth: Growth rates, yields, nutrient content.
Fish growth: Growth rates, feed conversion ratios, health.
Microbial activity: Analysis of microbial populations and nutrient transformations within the sand biofilter.

This comprehensive data collection allowed for a thorough understanding of the system’s dynamics and its effectiveness in achieving its intended goals.

Peer Review and Publication: The results of the iAVs research were subjected to peer review, a critical process in scientific validation where experts in the field evaluate the research methodology, data analysis, and conclusions. The findings were then published in multiple peer-reviewed scientific journals, further establishing the credibility and scientific rigor of the iAVs approach.

Why This Matters:

Evidence-Based Approach: The use of the scientific method ensured that iAVs was not based on anecdotal evidence or personal opinions, but on rigorous experimentation and data analysis. This makes iAVs a more reliable and trustworthy system compared to other aquaponics methods that often lack scientific validation.
Optimized Design: The research conducted at NCSU provided valuable insights into the optimal design and operating parameters for iAVs, ensuring its efficiency and effectiveness. Factors such as tank-to-biofilter ratios, irrigation cycles, and fish stocking densities were carefully studied to maximize both plant and fish production.
Understanding of Biological Processes: The detailed research on iAVs significantly advanced our understanding of the complex biological interactions within aquaponics systems. The role of sand as a habitat for beneficial microbes and its crucial role in nutrient cycling were thoroughly investigated. This knowledge is essential for creating stable and productive systems.

Contrasting Examples:

In contrast to iAVs’ scientific foundation, other aquaponics systems, like the Speraneos’ gravel-based system, were developed based on anecdotal observations and personal modifications, often without proper scientific validation. This led to the widespread adoption of less efficient and less sustainable systems, highlighting the importance of iAVs’ rigorous scientific approach.

Dr. McMurtry criticizes the lack of scientific rigor in the broader aquaponics community. He argues that many practitioners rely on anecdotal evidence, personal opinions, and marketing hype rather than verifiable data and controlled experiments. He expresses frustration with the lack of replication studies and the reluctance to adhere to the scientific method, which he sees as essential for advancing aquaponics as a legitimate and sustainable food production method.

While James Rakocy has undoubtedly contributed to the development of aquaponics, a closer examination of his work reveals discrepancies between scientific research standards and the presentation of his findings. A common criticism of Rakocy’s work is the misrepresentation of experimental demonstrations as rigorous scientific research. Demonstrations simply showcase the feasibility of a concept, while true scientific research involves controlled experiments and replication. Many of Rakocy’s studies at the University of the Virgin Islands (UVI) were essentially demonstrations lacking the necessary replication and statistical analysis to draw valid scientific conclusions. This raises concerns about the generalizability and reliability of his findings.

Rakocy often receives credit for pioneering the Deep Water Culture (DWC) or “raft” system. However, this concept originated with Ron Zweig and Bill McLarney at the New Alchemy Institute in the mid-1980s, predating Rakocy’s work. This misattribution illustrates a lack of proper acknowledgement of prior work.

Rakocy’s publications often omit essential financial information, including capital costs, operating expenses, and marketing costs. This lack of transparency makes it impossible to assess the true profitability of his systems, a critical factor for farmers and investors. Dr. McMurtry alleges that Rakocy misrepresented rainfall levels at his UVI research facility, leading to inflated claims about water efficiency. By failing to account for significant rainfall, Rakocy’s findings present an inaccurate picture of his systems’ water usage.

Presenting demonstrations as research without adhering to scientific methodology and omitting critical financial data can be misleading and detrimental to the field of aquaponics. It creates a false sense of certainty and can lead to the adoption of systems that may not be as efficient or profitable as claimed. This underscores the importance of critically evaluating claims and demanding transparency and rigor in aquaponics research.

“Sandponics”: A Misnomer and a Separate Technique

IAVS has, in recent years, been mistakenly referred to as ‘Sandponics’ due to the proliferation of social media. This is a critical misnomer that needs clarification. ‘Sandponics’ is actually a very different system of agriculture that was developed and trademarked in Japan and has no relation or similarity to IAVS other than the use of sand (Baba 2015). A lack of proper literature review by many researchers has led to the continuation of many errors and misconceptions. This exemplifies the need for proper, standard nomenclature. Dr. McMurtry himself prefers to avoid using “ponics” terminology altogether, arguing that the root word implies “toil, labor…suffering” which is not reflective of the IAVS approach.

This confusion is detrimental to the understanding and recognition of IAVS as a distinct and pioneering system. It is crucial to emphasize that IAVS is not a variation of “Sandponics”. Using the correct terminology ensures that IAVS receives proper recognition for its unique features and origin.

The Importance of Proper Nomenclature

Aquaponics, in its accepted standard definition, combines aquaculture (raising aquatic animals) with hydroponics (soilless plant cultivation). IAVS, however, integrates aquaculture with horticulture, specifically utilizing sand as a biofilter and growing medium. This difference is significant as it underscores IAVS’s emphasis on natural, soil-based processes, creating a more holistic and sustainable ecosystem compared to conventional aquaponics systems.

Using precise terminology is essential in the field of aquaponics, especially when distinguishing IAVS from other systems. Failing to do so leads to confusion, the spread of misinformation, and ultimately hinders the progress and understanding of IAVS. Proper nomenclature ensures clear communication, facilitates accurate research, and empowers informed decision-making. It is crucial for establishing aquaponics as a credible scientific discipline and promoting the adoption of the most effective and sustainable systems, such as IAVS (Palm 2024).

When people fail to adhere to proper nomenclature in the field of aquaponics, confusion and the spread of misinformation arise. This is clearly demonstrated in the case of “Sandponics,” a term often mistakenly used to refer to iAVs.

Here’s a breakdown of the consequences when people don’t use precise terminology, particularly confusing “Sandponics” with iAVs:

Undermining iAVs’ Originality and Scientific Foundation: iAVs, developed through rigorous scientific methodology, risks being overshadowed or misrepresented as a simple variation of a Japanese hydroponic technique. This disrespects Dr. McMurtry’s pioneering work and the unique features of iAVs.
Hindered Research and Development: When researchers use inaccurate terms, it becomes difficult to track the evolution and effectiveness of different systems. This can lead to the misapplication of findings and impede the progress of aquaponics as a legitimate field of study.
Misleading Practitioners: Confusing terminology can lead individuals to adopt methods that are not suitable for their needs or expectations. For example, someone seeking the benefits of iAVs’ organic, soil-based approach might mistakenly believe “Sandponics” offers the same advantages. This can result in disappointment and wasted resources.
Perpetuation of Inefficient Practices: The Speraneos’ gravel-based system, popularized partly due to a lack of proper nomenclature, illustrates the dangers of deviating from the scientifically validated iAVs design. If “Sandponics” is mistakenly seen as synonymous with iAVs, the gravel-based system’s drawbacks, such as reduced filtration and microbial activity, might be wrongly attributed to iAVs. This could discourage the adoption of the more efficient and sustainable iAVs approach.
Erosion of Scientific Credibility: The misuse of scientific terms undermines the credibility of the entire field. Aquaponics already faces skepticism from some quarters due to the prevalence of anecdotal claims over scientific evidence. Confusing terminology only exacerbates this problem, making it harder to establish aquaponics as a legitimate and respected field of study and practice.

The importance of proper nomenclature cannot be overstated. It’s crucial for:

Clear Communication: Ensuring that everyone involved in aquaponics is using the same language to accurately describe systems, methods, and results.
Effective Research: Facilitating accurate research, literature reviews, and comparisons between different systems. This allows for the identification of best practices and the advancement of knowledge.
Informed Decision-Making: Empowering practitioners to make informed choices about the systems they implement based on a clear understanding of their differences and potential benefits.

IAVS: Overlooked and Overshadowed

The history of iAVs reveals a frustrating paradox: a groundbreaking, scientifically validated system, invented before the widespread adoption of the term “aquaponics,” is now largely overshadowed by less efficient systems that emerged later. A confluence of factors, including the Speraneos’ modifications, the rise of the internet, and a general lack of thorough research in the aquaponics community, has contributed to this unfortunate situation.

Here’s a step-by-step explanation:

iAVs: A Precursor to Modern Aquaponics: Dr. Mark McMurtry developed iAVs in the mid-1980s, a time when the term “aquaponics” was not yet widely used. His system, based on rigorous scientific methodology and utilizing sand as a biofilter and growing medium, represented a significant advancement in integrated food production.
The Speraneos and the Gravel Substitution: The Speraneos, inspired by McMurtry’s work, decided to build their own system but used sand instead of gravel, a crucial deviation from the iAVs design. McMurtry, while overseas at the time, later attempted to persuade them to use sand or conduct comparative studies, but was unsuccessful.
The Rise of the Internet and the Spread of Misinformation: The Speraneos’ gravel-based system coincided with the emergence of the internet. They began promoting their modified system online, and it quickly gained popularity. This online dissemination, while beneficial for spreading awareness, also facilitated the spread of misinformation and misconceptions about aquaponics, obscuring the original, scientifically validated iAVs.
A “Tipping Point” and the Dominance of the Flood and Drain System: The Speraneos’ gravel-based system became the foundation for what is now widely known as the flood-and-drain aquaponics system. This system, despite being less efficient than iAVs in terms of filtration and nutrient cycling, became the dominant model due to its simplicity and early online promotion. The substitution of gravel for sand became a “tipping point,” leading aquaponics down a path of less efficient and less sustainable practices.
Perpetuation of Misconceptions and Reinventing the Wheel: The widespread adoption of the less efficient flood-and-drain system, coupled with inadequate literature review and a lack of adherence to the scientific method within the aquaponics community, has led to a cycle of repeating misconceptions and attempting to solve problems that iAVs had already addressed. The aquaponics field, in many ways, is reinventing the wheel, spending time, effort, and resources on issues that were already resolved by iAVs decades earlier.

Despite its proven effectiveness, IAVS has been overlooked and overshadowed by less efficient systems. The lack of proper nomenclature, the Speraneos’ modifications, and the uncritical adoption of information online have all contributed to this situation.

This highlights the crucial need for:

Thorough Literature Reviews: To accurately understand the history and development of different aquaponics systems and avoid perpetuating misconceptions.
Adherence to the Scientific Method: To ensure that systems are based on evidence and validated through rigorous experimentation rather than anecdotal observations.
Proper Nomenclature: To avoid confusion and accurately represent the unique features and origins of different systems.

The iAVs story is a cautionary tale about the importance of scientific rigor, accurate information dissemination, and the need to learn from the past to avoid repeating mistakes and hindering the progress of sustainable food production methods.

As a result, researchers and practitioners are grappling with challenges that Dr. McMurtry’s iAVs effectively addressed decades ago. The lack of awareness and understanding of iAVs has led to a situation where the industry is expending resources to solve issues that iAVs had already overcome.

Addressing Modern Challenges: How IAVS Offers Solutions

Here are some key areas where iAVs offers solutions that the aquaponics industry is still struggling with:

Sludge Management:

iAVs Solution: iAVs utilizes the sand bed as a biofilter, allowing solid fish waste (sludge) to be directly incorporated into the system. The sand provides a habitat for a diverse microbial community that breaks down the sludge, converting it into nutrients that are readily available to the plants. This eliminates the need for separate sludge removal systems and transforms waste into a valuable resource.
Current Industry Struggles: Many aquaponics systems still rely on methods such as sedimentation, sieve separation, and foam fractionation to remove sludge. These methods can be complex, costly, and energy-intensive. Recent research is exploring complex solutions like anaerobic digestion and bacterial solubilization, all while overlooking the simple and effective approach that iAVs has offered for years.

Nutrient Imbalances:

iAVs Solution: The sand-based biofilter in iAVs promotes a rich and diverse microbial community that efficiently converts fish waste into plant-available nutrients. This results in a more balanced nutrient profile, reducing the risk of deficiencies or toxicities that can harm plants or fish.
Current Industry Struggles: Maintaining optimal nutrient balance remains a challenge in conventional aquaponics systems. Often, fish waste alone does not provide all the necessary nutrients for robust plant growth, leading to the need for supplementation. This adds complexity and cost to the system, and can disrupt the delicate balance of the aquaponics ecosystem.

Energy Efficiency:

iAVs Solution: iAVs minimizes energy use in several ways. The sand bed acts as a natural filter, reducing or eliminating the need for energy-intensive pumps and filtration systems. Additionally, iAVs systems typically only require the pump to run for a few hours each day, further reducing energy consumption.
Current Industry Struggles: Conventional aquaponics often involves complex filtration, aeration, and water circulation systems that consume significant amounts of energy. The industry continues to search for solutions to reduce energy consumption, often through more complex technologies, while a simple and effective approach like iAVs remains underutilized.

pH Stability:

iAVs Solution: The sand-based biofilter in iAVs, along with the system’s design, contributes to stable pH levels. This stability is crucial for the health of both fish and plants.
Current Industry Struggles: Maintaining optimal pH balance can be challenging in traditional aquaponics systems due to the accumulation of acidic byproducts from fish waste. Constant monitoring and adjustments are often required, adding to the complexity and labor involved in managing the system.

Simplification and Resource Efficiency:

iAVs Solution: iAVs is designed for simplicity and efficiency. It minimizes the need for complex equipment, external inputs, and labor-intensive management practices. The system effectively utilizes natural processes to create a sustainable and resilient food production ecosystem.
Current Industry Struggles: Many aquaponics systems have become increasingly complex, involving intricate filtration, monitoring, and control systems. This complexity can make aquaponics less accessible and less appealing, particularly for small-scale farmers or those in resource-limited settings.

The lack of awareness of iAVs within the aquaponics community represents a significant missed opportunity. Researchers and practitioners are often re-exploring solutions that iAVs has already effectively provided.

This highlights the crucial need to:

Re-evaluate Existing Knowledge: A thorough examination of the iAVs research is essential to learn from past successes and avoid repeating mistakes.
Promote Accurate Information: Disseminating accurate information about iAVs and its benefits is crucial to counteract the spread of misinformation and misconceptions that have contributed to its obscurity.
Embrace Simplicity and Sustainability: Shifting the focus towards simpler, more sustainable, and energy-efficient systems like iAVs will enhance the viability and appeal of aquaponics as a solution for global food security.

The Iron Supplementation Misconception: A Case Study in Overlooking IAVS

The history of aquaponics reveals a persistent misconception: the belief that essential nutrients, like iron for example, must be supplemented for successful plant growth. This misconception stems from the widespread adoption of aquaponics systems that remove solid fish waste, thereby depriving the system of a valuable source of nutrients. However, Dr. McMurtry’s Integrated Aqua-Vegeculture System (iAVs), a pioneering approach that utilizes all fish waste solids, demonstrated that iron supplementation is often unnecessary. Sadly, iAVs has been largely overlooked, leading to the perpetuation of this misconception.

Most of the nutrients available for plant uptake accumulate in the solid part of the fish ‘waste’ and so systems that do not utilize all of that waste will not have adequate nutrients (Schneider et al., 2005; Neto & Ostrensky, 2013). Utilization of all the fish solids is why IAVS is a closed-loop system that saves water and minimizes waste (Delaide et al., 2015; Delaide 2018). Utilization of the solid fish ‘waste’ provides economic benefits and address the future scarcity of non-renewable fertilizers (Ezziddine 2020).

Here’s a closer look at how this situation developed:

Early Aquaponics Research and Nutrient Removal: Early aquaponics research often focused on systems that removed solid fish waste. This approach, while seemingly simplifying the system, resulted in the loss of valuable nutrients, including iron. To compensate for these losses, researchers and practitioners resorted to nutrient supplementation, establishing a practice that continues to this day.
iAVs: A Paradigm Shift in Nutrient Management: Dr. McMurtry’s iAVs challenged this convention by incorporating all fish waste solids into the system. The sand-based biofilter effectively breaks down the solid waste, releasing a wide spectrum of nutrients, including iron, in forms readily available to plants. Research on iAVs demonstrated that this holistic approach provided sufficient iron for healthy plant growth without the need for supplementation.
The Obscuring of iAVs and the Persistence of Misconceptions: Despite its effectiveness, iAVs has been overshadowed by less efficient systems that gained popularity due to factors such as the Speraneos’ modifications and the rise of the internet. The lack of awareness of iAVs within the aquaponics community has led to the continued misconception that iron supplementation is essential.

The case of iron supplementation in aquaponics exemplifies the broader issue of overlooking iAVs and its valuable contributions to the field. To correct this course, the aquaponics community needs to:

Revisit the iAVs Research: A thorough understanding of iAVs and its principles is essential to dispel misconceptions and learn from past successes.
Embrace Holistic Nutrient Management: Recognizing the value of utilizing all fish waste solids can lead to more balanced and sustainable aquaponics systems that minimize the need for supplementation.
Promote Accurate Information Sharing: Raising awareness of iAVs and its benefits can help correct misinformation and encourage the adoption of more effective and sustainable practices.

The Visionary Origins of IAVS

The invention of iAVs was driven by the need for more sustainable and efficient methods of food production, particularly in regions with limited resources. Traditional aquaculture systems often face challenges such as maintaining water quality, managing waste, and relying on external inputs like fertilizers. iAVs was designed to address these issues by integrating fish and vegetable production in a closed-loop system that mimics natural nutrient cycles (McMurtry 1997b).

Dr. McMurtry was deeply concerned about global issues such as poverty, environmental degradation, and the potential for future food shortages. He envisioned iAVs as a tool to address these challenges, particularly in regions like Africa, where food insecurity and resource scarcity were prevalent. His commitment to a sustainable future for humanity and his focus on creating a system that could provide complete nutrition while minimizing environmental impact were central to the invention of iAVs.

Here are the key factors that led to the development of iAVs:

The need for improved methods to produce high-quality protein and vegetable foods with limited resources.
Addressing the problems of maintaining sufficient oxygen in biofilters, clogging, and channeling in traditional recirculating aquaculture systems.
Reducing reliance on expensive microbial denitrification and partial flushing for nitrate and phosphate control.
Overcoming the issue of sedimentation sequestering nutrients and making them unavailable to plants, leading to a dependence on fertilizer amendments (McMurtry 1997b).
Addressing the Growing Need for Food and Water: In the 1980s, it was becoming evident that traditional agriculture was on an unsustainable trajectory. The world faced a rapidly growing population, leading to increased pressure on finite resources like water and fertile land. This urgency for a more efficient and sustainable food production method, particularly in water-scarce regions, was a key motivator for Dr. McMurtry.
Overcoming the Limitations of Traditional Aquaculture: Existing aquaculture methods, especially intensive systems, relied heavily on water for maintaining oxygen levels and removing waste. These practices were unsustainable, particularly in arid and semi-arid climates already grappling with water scarcity. iAVs was envisioned as a way to reduce water dependency in fish farming by integrating it with plant production, creating a closed-loop system where water is recirculated and reused.
Finding Solutions for Waste Management and Nutrient Recovery: Traditional aquaculture often involved discharging nutrient-rich wastewater into the environment, leading to pollution and ecological imbalances. iAVs aimed to tackle this by using plant roots to uptake the excess nutrients from fish waste, effectively closing the nutrient loop within the system. This approach minimized waste, reduced the need for external fertilizers, and promoted a more sustainable and environmentally friendly approach to food production.
Creating a Simpler and More Accessible System: iAVs was intentionally designed for simplicity, relying on natural processes and minimizing the need for complex technology or expensive inputs. Dr. McMurtry’s vision was to create a system that would be accessible and affordable, particularly for small-scale farmers and communities in developing countries where resources were limited.
Addressing Land Availability Constraints: iAVs offered a solution for regions with limited arable land. Unlike traditional pond or cage aquaculture, iAVs could be implemented in various settings, even those with poor soil quality or limited space. This versatility made iAVs particularly relevant for urban environments and regions facing land scarcity.

Reasons why it was invented

Mark McMurtry states that iAVs was invented to help people improve their food security, especially those in challenging environments, such as arid regions. He designed the system to be simple, low-tech, and adaptable to non-electrified, resource-poor areas. McMurtry emphasizes that iAVs is “about people who needed a better/more reliable diet,” and that his intention was for them to be able to improve their lives and have more food security in difficult situations. He believes that iAVs is not about the technology or equipment, but rather about “biology and common sense.” McMurtry also wanted iAVs to be open-source so that it could be freely used to benefit anyone who needed it.

McMurtry wanted iAVs to be readily transferable to the developing world, which influenced his research decisions. For example, he explains that his research was not focused on maximizing productivity, but rather on establishing the relationships between the different components of the system. He explicitly states that the focus of the research was to determine “how much of what type of crops can be produced from a unit (kg increase) of fish growth,” and not on achieving the highest possible yields.

The invention of IAVS was driven by a number of factors, primarily focused on addressing challenges related to water scarcity, food security, and sustainability (McMurtry 1997a).

Growing Population and Water Scarcity: The world faces a rapidly growing population, putting strain on resources, particularly in arid and semi-arid climates already struggling with desertification and famine. This necessitates research into more efficient methods for food production, especially those that conserve water (McMurtry 1997a).
Inefficient Water Use in Traditional Aquaculture: The aquaculture industry has historically relied heavily on water, particularly intensive systems that require continuous flows for oxygenation and waste removal. These practices are unsustainable in the face of growing water scarcity, highlighting the need for alternative approaches (McMurtry 1997a).
Potential for Integration and Water Reduction: Integrating aquaculture with agriculture offers a solution by reducing water demand and maximizing resource utilization. IAVS uses fish waste as a direct input for vegetable production, eliminating the need for separate water and fertilizer systems. These systems can operate with significantly less water than traditional pond or cage aquaculture, making them suitable for areas with limited water resources (McMurtry 1997a). McMurtry’s system used only 1 percent of the water needed for pond aquaculture (Mandal 2023).
Nutrient Recovery and Waste Management: Traditional recirculating aquaculture systems often rely on water exchange to control nutrient buildup, resulting in water waste and environmental concerns. IAVS addresses this issue by incorporating hydroponic plant culture, allowing plants to absorb excess nitrates and phosphates from fish waste. This reduces the need for water exchange and minimizes nutrient discharge into the environment (McMurtry 1997a).
Synergistic Benefits: IAVS offer a synergistic approach to food production, yielding both high-quality protein from fish and fresh vegetables. This integrated system aims to address both dietary needs and market demands, particularly in regions facing food insecurity (McMurtry 1997a).
Simplicity and Sustainability: IAVS are designed for functional and technological simplicity, reducing reliance on complex filtration or chemical inputs. The use of sand beds as biofilters, plant substrates, and solid waste treatment areas further enhances the system’s efficiency and sustainability (McMurtry 1997a).
Addressing Land Availability Constraints: The iAVs is not limited by soil type or land availability, unlike pond or cage aquaculture systems. This makes it a versatile option for various geographical locations, particularly those with limited arable land (McMurtry 1990c).

IAVS Design and Functionality

The iAVs system aims to achieve the following objectives:

Functional simplicity and ease of maintenance and operation.
Improved water and nutrient utilization efficiency.
Control of nitrate and phosphate levels through plant uptake, reducing the need for water flushing (McMurtry 1997b).

The researchers behind iAVs specifically sought to design a system that would be low-tech, low-input, and high-yielding. By leveraging the symbiotic relationship between fish and plants, iAVs reduces the need for external inputs like fertilizers and lime, minimizes water consumption, and promotes efficient nutrient cycling (McMurtry 1997b).

Previous integrated fish vegetable systems have also removed suspended solids from water by mechanical filtration prior to plant application. Acceptable fruit yields in such systems have been achieved with substantial supplementation of plant nutrients (Lewis et al. 1978, 1981; Rakocy 1989; Goddek et al. 2019; Ezziddine 2020).

The byproducts of fish contain a significant amount of essential nutrients, and failing to utilize them results in their loss (Jung and Lovitt 2011; Goddek et al. 2016; Gilbert 2009; (Seawright et al. 1998; Schneider et al. 2005; Neto and Ostrensky 2013;Delaide et al. 2019 ).

Biodigestion of the fish sludge via heterotrophic bacteria, in a process, called nutrient solubilisation or mineralisation, the macro- and micronutrients bound to the organic matter (OM) are released. Heterotrophic bacteria degrade the sludge under aerobic conditions, (Delaide et al. 2019). where the sludge is in constant contact with oxygen, which is used for bacterial respiration, producing the oxidation of the OM. Some of the main advantages of the aerobic treatment compared to anaerobic treatment are the non-production of toxic compounds for plants or fish, and the faster sludge reduction performance which can then be utilized by the plants (Chen et al. 1997; Delaide et al. 2019; Delaide et al. 2019b). This process of nutrient solubilization, or mineralization, is similar to what happens in soil-based systems such as IAVS.

The introduction of the reciprocating biofilter, in which filter beds are alternately flooded and drained, has reduced problems of clogging, channelization and low oxygen (Lewis et al. 1978; Paller and Lewis 1982), opening the possibility of retaining the solids as nutrient resource for plant growth (McMurtry et al. 1997).

Aerobic digestion is a process where microorganisms break down organic matter in the presence of oxygen, this process effectively mobilizes nutrients from solid waste, making them available for plant uptake. The process of aerobic digestion significantly increases the amount of macro and micronutrients available for plant uptake (Ezziddine 2020). By directly utilizing fish waste, IAVS eliminates the need for separate waste treatment and external fertilizers. This closed-loop system conserves resources and reduces environmental impact. Aerobic decomposition rapidly breaks down organic matter, leading to faster plant growth and higher yields. By treating waste within the system, IAVS promotes sustainable agriculture by reducing reliance on external inputs and minimizing waste generation.

Sand serves as a mechanical filter, removing suspended organic matter from the recirculating water. This filtration is crucial for maintaining water quality and promoting fish health. The research specifically investigated the effectiveness of sand in combination with plants for water filtration, a novel approach not previously documented. This system offers several benefits, including the conservation of soil, water, and plant nutrients; the availability of high-quality food near population centers; and reduced operating costs compared to either cropping system alone (McMurtry 1987).

IAVS is designed for functional and technological simplicity. Fish effluents, including solids, are pumped directly onto sand beds which act as biofilters, plant growth substrate, and the location for the oxidation of organic solids. (McMurtry 1997a). The fish produce waste, uneaten food, and dead algae that serve as nutrients for the vegetable crops. These sand beds act as a biofilter, removing dissolved and suspended organic matter from the fish tank water. Builder’s grade sand is used as the growing medium for the vegetables. No additional nutrient amendments are added to the sand beds as the fish waste provides the necessary nutrients (McMurtry 1987). They found that tissue concentrations of major nutrients such as N, P, K and Mg were not limiting. This indicates that irrigation with fish wastewater can provide nutrients for tomato production. Palada supports the results obtained by McMurtry et al. (1993a) who reported that tissue concentrations of N, P, K and Mg were not limiting in tomato irrigated with recirculating aquaculture water (Palada 1999)

The filtered water then drains back into the fish tanks by gravity (McMurtry 1993b).

Fish Tank:

The system begins with a tank specifically designed for raising fish, typically tilapia. This tank serves as the primary habitat for the fish and houses the water that will be circulated throughout the system (McMurtry 1990a). The bottom of the tank is sloped to a central point, this slope serves a crucial function: it directs the flow of water and solid waste towards a specific point, where the water pump (or pump intake) sits, facilitating the collection and transfer of fish effluent to the biofilters. By concentrating the water at a low point, the pumps could easily draw water from the tanks and transfer it to the biofilters (McMurtry 1997a, 1997b). The water from the fish tanks, which contains dissolved and suspended organic materials, is then used to irrigate biofilters containing vegetables such as tomatoes. The biofilters, which use materials like builder’s grade sand as a substrate, help to remove excess nutrients from the water. This process benefits both the fish and the plants: the fish benefit from the removal of waste products from their water, while the plants receive nutrients from the fish waste (McMurtry 1993a).

Enhanced Oxygenation:

The rapid drainage ensures that the sand bed is not constantly submerged in water. This allows for atmospheric gas exchange, replenishing oxygen levels in the root zone and promoting aerobic decomposition of organic matter. Each dewatering cycle effectively “recharges” the filter with oxygen, benefiting both the nitrifying bacteria and plant root health. This is crucial for maintaining a healthy microbial community and supporting optimal plant growth.

Furrows, Ridges, and Clogging in IAVS

Prevention of Waterlogging and Root Rot: The slope ensures that water does not pool in the biofilter, preventing waterlogging and creating a more favorable environment for plant roots. Prolonged water saturation can lead to root rot and negatively impact plant health and productivity.
Efficient Nutrient Cycling: The rapid drainage and subsequent long interval between irrigation cycles create a reciprocating flow that enhances nutrient cycling. This alternating pattern of flooding and drying allows for a more even distribution of nutrients throughout the sand bed and prevents nutrient buildup in specific areas.

The long interval between irrigation cycles further contributes to the system’s effectiveness:

Maximizes Nutrient Absorption: The extended dry periods allow plant roots to absorb nutrients more effectively. Constant saturation can hinder nutrient uptake and create an imbalance in the system.
Reduces Energy Consumption: The less frequent need for pumping water reduces energy consumption, contributing to the overall sustainability and cost-effectiveness of the system.
Promotes Microbial Activity: The dry cycles allow beneficial bacteria in the sand bed to thrive and perform their essential functions, like nitrification, more efficiently.

The water from the fish tanks is pumped to the biofilters, where it is distributed evenly throughout the filtration medium. The plants in the biofilters take up the nutrients from the water, helping to maintain water quality within acceptable limits for the fish. The filtered water then drains back into the fish tanks, completing the cycle (McMurtry 1993a).

The choice of sand was due to its:

Inert Nature: Builder’s grade sand is relatively inert, providing a stable and controlled environment for plant growth without introducing extraneous nutrients.
Drainage Properties: Sand has excellent drainage properties, preventing water logging and ensuring proper aeration for plant roots.
Filtration Capacity: The sand particles provide a large surface area for microbial colonization, facilitating biological filtration and nutrient cycling.(McMurtry 1990a).

The biofilters are sloped to direct drainage back to the fish tank (McMurtry 1997a).

Growing Medium: The sand provides a stable, well-aerated substrate for the plant roots to grow and thrive. The sand acts as a natural filter, removing fish waste products and uneaten feed from the water (McMurtry 1990a). The specific composition of the sand is important to avoid clogging (McMurtry 1997a).
Water Circulation System: A crucial aspect of IAVS is the circulation of water between the fish tank and the sand beds. This circulation is typically achieved using a pump that draws water from the bottom of the fish tank and delivers it to the sand beds. A timer is used to control the irrigation schedule. Water is drawn from the bottom of the fish tanks and pumped to the biofilters eight times daily to ensure a constant supply of nutrients to the plants and effective filtration of the water. The cascading drainage of water back into the fish tank from the elevated sand beds increases aeration of the fish tank water. (McMurtry 1990a, 1997a).

The Role of Sand as a Biofilter

The use of sand as a biofilter is a defining characteristic of IAVS, distinguishing it from other integrated systems like aquaponics. The sand provides several benefits:

Mechanical Filtration: The sand’s physical structure traps solid waste particles, such as uneaten fish food and fish excrement, preventing them from accumulating in the water (McMurtry 1990a).
Microbial Nitrification: The sand serves as a habitat for beneficial bacteria that play a vital role in converting harmful ammonia, a byproduct of fish waste, into nitrates. Nitrates are a form of nitrogen that plants can readily absorb as nutrients (McMurtry 1990a).
Aeration: The porous nature of sand allows for good air circulation within the bed, providing essential oxygen to the plant roots and the beneficial bacteria responsible for nitrification (McMurtry 1990a). The reciprocating flow of water through the sand beds enhances aeration, providing oxygen to both plant roots and nitrifying bacteria. The drainage cycle allows for complete atmosphere exchange within the sand, promoting healthy root development and efficient microbial activity (McMurtry 1987).

Sand Beds:

The vegetable crops are cultivated in specially constructed beds (biofilters) filled with sand. The growing medium for the vegetables was “builder’s grade sand” composed of 98.3% quartz sand and 1.7% silt. (McMurtry 1990a).

The sand beds act as biofilters, providing a substrate for beneficial bacteria that break down organic waste from the fish tanks. The reciprocating flow of water through the sand bed (alternating flooding and draining) ensures efficient oxygenation and nutrient cycling within the biofilter, fostering bacterial growth and waste breakdown. The sand beds also function as the growth medium for the plants, providing physical support for the plants while the nutrients required for growth are primarily supplied through the water. The system is designed to pump fish effluent, including solids, directly onto the sand beds. The sand acts as a filter, trapping solid waste particles, and the microbial activity within the sand bed facilitates the decomposition of these solids, converting them into nutrients available for plant uptake (McMurtry 1997a).

Sand particles have spaces between them, allowing water to flow through the biofilter and ensuring good drainage. This porosity is important for both plant roots and nitrifying bacteria, which need access to oxygen.

Support for Plant Roots: Sand provides physical support for tomato plants’ root systems, anchoring them securely in the biofilter.
Surface Area for Bacterial Growth: The surface of sand particles provides ample space for beneficial nitrifying bacteria to colonize. These bacteria play a key role in converting harmful ammonia from fish waste into less toxic nitrates, which plants can then utilize as nutrients.
Nutrient Retention: While allowing water to pass through, sand also retains some nutrients, making them available to plant roots (McMurtry 1993b).
Mechanical Filtration: The sand’s particle size and structure effectively trap solid waste from the fish, preventing it from accumulating in the water and harming the fish or disrupting the system’s balance. The sand acts as a sieve, capturing the solid particles while allowing the water to pass through. This process is crucial for maintaining water clarity, reducing the breakdown of solids into smaller, potentially harmful particles, and promoting a healthy environment for the fish.

Aeration and Drainage: The spaces between the sand particles promote excellent drainage, preventing water logging and ensuring that plant roots have access to the oxygen they need to thrive. The reciprocating flow of water, flooding and draining the sand bed, further enhances aeration and supports healthy root development.
Nutrient Retention and Availability: While allowing water to flow through, the sand also retains essential nutrients, making them readily available to plant roots. The sand acts like a natural reservoir, holding the nutrients released from the breakdown of fish waste and preventing them from being washed away, ensuring a consistent supply for the plants.
Stability and Support: The sand provides a stable and supportive environment for plant roots to anchor themselves and grow. This is particularly important in iAVs, where plants play a crucial role in nutrient uptake and water filtration.

The Importance of Particle Size:

The selection of medium-coarse sand is crucial for achieving optimal results in iAVs. Finer sand particles would be more prone to compaction, leading to poor drainage and potential clogging, while larger particles would not provide sufficient surface area for bacterial colonization or nutrient retention. The use of gravel, a common practice in many aquaponics systems that deviated from Dr. McMurtry’s original iAVs design, has proven to be far less effective for both filtration and plant growth, leading to a variety of challenges, including reduced system efficiency, nutrient deficiencies, and increased maintenance.

When gravel is used instead of sand in an iAVs system, the smaller, broken-down fish waste particles can recirculate back into the fish tank, potentially causing harm to the fish. This is because gravel, with its larger particle size and gaps, lacks the filtration capacity of sand. When gravel is used as a growing medium, the larger gaps between the particles allow the suspended solids to pass through, bypassing the crucial mechanical filtration stage. The gravel does not effectively trap the smaller waste particles, allowing them to return to the fish tank along with the water. The recirculation of these fine particles can have detrimental effects on the fish. The particles can irritate or damage the delicate gills of the fish, potentially leading to respiratory problems. If the particles come into contact with the fish’s eyes, they can cause irritation, inflammation, and even infections.

The biofilters have a sloped bottom with a gradient of 1/200 along the length. This slight slope is designed to facilitate drainage of the water and is crucial for ensuring proper drainage of the water back into the fish tanks after it had percolated through the sand bed. The slope prevented water from pooling in the biofilters, ensuring that the water consistently flowed back to the fish tanks, completing the circulation loop. (McMurtry 1997a, 1997b).

Furrows

Furrows are shallow trenches or channels dug into the soi and play a crucial role in directing the flow of nutrient-rich water from the fish tank to the plant roots within the sand beds. Water pumped from the fish tank is channeled directly into these furrows, ensuring a concentrated flow of nutrients to the root zone. This targeted irrigation maximizes nutrient availability for the plants.

Water from the fish tank is pumped to the sand beds through furrows and play a role in concentrating nutrients where they are most accessible to plant roots. In the IAVS research there was a nutrient gradient in the sand beds, with higher concentrations of phosphorus, potassium, and manganese found closer to the furrows. The paper notes that “P, K, and Mn concentrations were greatest nearest the furrow and at the surface.” (McMurtry 1987).

Ridges

Ridges are raised rows of soil or growing medium created between furrows. In agricultural practices, ridges and furrows are often used together to manage water and improve soil conditions.

Ridge furrowing is where various widths of ridges are built in the field and alternating with corresponding furrows. The soil from furrows is added to the counterpart ridges to channelize rainwater into furrows and

to minimize surface water runoff. This system has proved effective in arid to semiarid areas where precipitation is the sole source of water for agricultural production (Zhou et al., 2009).

A number of studies have determined the effect of ridge-furrow planting configuration on the root characteristics of field crops (Chakraborty et al., 2008; Gao et al., 2005a; Niu et al., 2004; Rahman et al., 2005; Ren et al., 2010). Nearly all have shown that the RF system improves root development and distribution in soil.

Ridges facilitate the flow of water through the furrows, preventing waterlogging and ensuring that excess water drains away from the plant roots. This is crucial in a sand-based system where drainage is essential to maintain proper aeration for plant roots. The raised structure of ridges promotes better air circulation within the growing medium. Ridges, combined with furrow irrigation, enable targeted nutrient application. The nutrients from the fish effluent are delivered directly to the root zone, maximizing uptake efficiency and minimizing nutrient loss.

Clogging

The researchers describe using “builder’s grade sand” as the substrate for the biofilters. Builder’s grade sand is known for its relatively large particle size. This characteristic makes it less susceptible to compaction and clogging compared to finer-grained materials.

Moreover, the researchers employed a “reciprocating biofilter” design, which alternately floods and drains the sand bed. This regular cycle of wetting and drying helps to prevent the buildup of organic matter and maintain good aeration within the substrate. These design features likely mitigated the risk of clogging in the biofilters, ensuring the efficient flow of water and nutrients to the plants.

Benefits of IAVS

Benefits of using IAVS for food production include:

Buffering Capacity: The accumulation of organic matter in the sand beds contributes to their buffering capacity, helping to stabilize pH levels. This buffering effect reduces the need for frequent alkaline amendments to counteract the acidifying nature of the nitrification process (McMurtry 1987).
Resource Conservation: IAVS excels in conserving both water and nutrients. By recirculating the water, IAVS significantly reduces water consumption compared to traditional fish farming methods. Furthermore, the system minimizes the need for external fertilizers as the fish waste naturally provides nutrients for the plants (McMurtry 1990a). iAVs conserve soil, water resources, and plant nutrients, making them particularly suitable for areas where these resources are limited. Recirculating systems use less water needed for equivalent fish yields in pond culture. This conservation is beneficial in arid, semi-arid, and tropical regions facing high demand for fish and fresh vegetables (McMurtry 1987).
Increased Productivity: IAVS demonstrates the potential to achieve higher yields of both fish and vegetables compared to conventional methods. The continuous nutrient supply from the fish waste, coupled with the efficient water and nutrient uptake by the plants, contributes to increased overall productivity (McMurtry 1990a).
Increased Yield: The consistent and balanced nutrient availability provided by the recirculating water, coupled with the efficient aeration during each irrigation cycle, may contribute to higher yields in iAVs compared to traditional methods. The study reported substantially increased yields for bush beans, cucumbers, and tomatoes in the iAVs compared to control plots and average US yields (McMurtry 1987).
Environmental Sustainability: IAVS minimizes its environmental impact and promotes sustainability by minimizing water usage and reducing reliance on chemical fertilizers The sand-based biofiltration system effectively removes organic matter from the water, thereby treating fish waste within the system, minimizing pollution and supporting healthy fish growth (McMurtry 1990a, 1987).
Improved Food Security: IAVS can play a significant role in enhancing food security, especially in regions facing water scarcity or limited access to resources. The system’s ability to produce both high-quality protein from fish and a variety of vegetables in a relatively small space makes it a valuable tool for improving food accessibility (McMurtry 1990a).
Localized Food Production: iAVs enable the production of high-quality food products close to population centers, ensuring readily available and fresh food supplies. This localized production reduces transportation costs and promotes food security (McMurtry 1987).
Economic Viability: The symbiotic co-production within iAVs leads to reduced operating costs compared to separate fish or vegetable cultivation. The fish waste provides nutrients for the plants, eliminating the need for expensive inorganic fertilizers. This cost reduction makes iAVs an attractive option for both small-scale and commercial operations (McMurtry 1987).
Market Potential: iAVs can target specific market demands, further enhancing their economic potential. Near urban areas, especially during winter in temperate regions, “organically” grown vegetables command premium prices. Fresh fish markets thrive in landlocked regions and overfished coastal areas worldwide (McMurtry 1987).
Cost-Effective Material: Builder’s grade sand, a readily available and inexpensive material, makes it a cost-effective option for iAVs implementation. The use of sand eliminates the need for more expensive substrates or complex filtration systems (McMurtry 1987).

Research Focus and Results in ‘Sand Culture of Vegetables using recirculating aquacultural effluents”

The primary objective of this research was to examine if an IAVS, specifically using sand beds for plant cultivation (“Sandponics”), could effectively support both fish production and vegetable growth without the need for external fertilizers. The researchers wanted to determine if vegetables grown in sand beds could adequately filter the recirculated water from the fish tank, providing the fish with clean water while simultaneously receiving sufficient nutrients from the fish waste (McMurtry 1990a).

The research successfully demonstrated the feasibility of the IAVS system for concurrent production of fish and vegetables without supplemental fertilization (McMurtry 1990a).

The study focused on the growth of three specific vegetable crops within the IAVS:

Bush bean (Phaseolus vulgaris L. cv. Bush Blue Lake 274)
Cucumber (Cucumis sativus L. cv. Burpee Hybrid II)
Tomato (Lycopersicon esculentum Mill. cv. Champion)

To provide a comparison point, they also cultivated these crops in a separate sandy loam soil bed amended with composted horse manure.

The yields obtained in the study demonstrate the potential of the IAVS to produce a substantial amount of food, especially considering the absence of additional fertilization in the sand-bed system. The researchers highlight the need for further investigation into factors influencing crop yield, such as nutrient availability, planting density, and environmental conditions, to optimize the system for maximum productivity.

Fish Growth and Water Quality: The system effectively maintained water quality suitable for tilapia growth, with parameters like nitrite and ammonia (which can be harmful to fish) remaining below toxic levels. The fish in the system exhibited healthy growth, with a feed conversion ratio of 1:1.3. Dissolved oxygen levels were noted to be lower than ideal for optimal fish growth, suggesting potential for improvement, however, the researchers aimed to assess the IAVS’s feasibility in arid regions like Africa, where access to sophisticated technology might be limited. Therefore, they deliberately chose not to incorporate additional aeration methods like air pumps or air stones. This decision aligns with their overall goal of evaluating the system’s performance in a “low-tech” environment. The cascading drainage from the sand beds back into the fish tank provides some degree of aeration, but the primary focus was on the sand’s capacity to support microbial communities that convert harmful fish waste products into plant-available nutrients. While the system maintained acceptable water quality for fish survival, optimizing DO levels could lead to enhanced fish growth rates(McMurtry 1990a).

Vegetable Yields: All three vegetable crops tested (bush bean, cucumber, and tomato) thrived in the sand beds, producing good yields despite experiencing heat stress. Yields for beans and cucumbers in the sand beds surpassed those of the control soil beds. Tomato plants in the sand beds produced a greater number of fruits compared to the soil beds, but high temperatures led to fruit abortion. The researchers intentionally removed the greenhouse shade fabric to subject the plants to elevated temperatures, simulating desert conditions. This was not an oversight or mistake; it was a deliberate aspect of the experimental design. This manipulation resulted in extremely high temperatures within the greenhouse, reaching up to 50 degrees Celsius which significantly exceeded the optimal range for tomato fruit development (McMurtry 1990a).

Nutrient Supply and Distribution: Despite the minimal nutrient levels in the recirculating water and the absence of added fertilizers, the IAVS system provided adequate nutrition for plant growth. The researchers attribute this to the system’s constant replenishment of nutrients from the fish waste. Analysis of plant tissue revealed that most nutrient levels were above deficiency thresholds, although some fell below optimal sufficiency levels, indicating potential areas for further optimization (McMurtry 1990a).

Water Conservation: The IAVS system exhibited excellent water conservation, with makeup water requirements averaging only 7% of the system volume per day (McMurtry 1990a).

Biofiltration Effectiveness: The sand beds functioned effectively as biofilters, maintaining water quality suitable for fish production. The sand-based filtration facilitated microbial nitrification, converting harmful ammonia from fish waste into nitrates that served as plant nutrients. Plant uptake of nitrogen compounds also contributed to controlling ammonia and nitrite levels. The sand bed serves as a biological filter, hosting a diverse community of microorganisms that play a crucial role in nutrient cycling. While nitrification (the conversion of ammonia to nitrates) is a prominent process, other microbial transformations contribute to nutrient availability, such as the mineralization of organic matter, which releases nutrients in forms that plants can readily absorb. The primary source of nutrients in the IAVS is the fish waste, which comprises a complex mixture of organic and inorganic compounds, including nitrogen (in various forms), phosphorus, potassium, and other essential elements. The composition of the fish feed ultimately contributes to the nutrient content of the fish waste (McMurtry 1990a).

Nutrient Accumulation and Distribution in the Sand: Nutrient levels in the sand increased with proximity to the irrigation furrow. The intermittent flooding and draining cycle not only facilitates nutrient cycling but also contributes to the physical distribution and accumulation of nutrients within the sand bed, making them accessible to plant roots (McMurtry 1990a).

Intermittent Irrigation: The researchers concluded that the reciprocating water movement in the IAVS system, characterized by intermittent pumping cycles, played a key role in its success. This intermittent flow led to:

Uniform nutrient distribution

Efficient oxygen supply to both plants and fish

The study proposes that further investigations explore the potential for increasing the ratio of fish biomass to crop bed area as a means to enhance nutrient availability to the plants. Additional research into the biological interactions and economic potential of the IAVS system is recommended (McMurtry 1990a).

Potential for Optimization: The researchers suggested that increasing the ratio of fish biomass to crop bed area, supplementing the sand medium, or using foliar applications could be ways to address potential nutrient limitations and further enhance plant growth (McMurtry 1990a).

The researchers prioritized evaluating the IAVS’s core functionality—biological filtration and nutrient cycling—under simulated desert conditions. They recognized the trade-offs associated with this approach, such as lower DO levels, but ultimately demonstrated the system’s viability in a resource-constrained environment.

It’s worth noting that the study primarily focuses on the proof-of-concept for an integrated system, and further research could explore optimizing various aspects, including DO levels, for enhanced productivity. The researchers suggest potential strategies for such optimization, like adjusting the fish stocking density or incorporating additional aeration methods, while considering the specific context and resource availability in the target environment.

In conclusion:

The research was conducted in a greenhouse with shade cloth intentionally removed to simulate the high temperatures of desert environments. This design choice underscores the researchers’ interest in adapting the IAVS for regions like Africa, where water scarcity poses a significant challenge to conventional agriculture.

The results demonstrate the system’s ability to produce both fish and vegetables with minimal water usage, offering a promising solution for arid environments. The emphasis is on developing a system that can be implemented with limited technological resources. This is evident in the deliberate decision to avoid using additional aeration methods like air pumps or air stones, relying instead on the cascading drainage from the sand beds for oxygenation. This approach aligns with the goal of making the IAVS accessible to communities in developing countries where access to sophisticated technology might be limited.

The primary reason for the study was to evaluate the feasibility and effectiveness of the IAVS as a sustainable food production model, particularly for arid regions with limited technological resources. The research demonstrates that this system can effectively integrate fish and vegetable production, conserve resources, and maintain acceptable water quality for both fish and plants without relying on external fertilizers. The researchers meticulously analyzed the nutrient content of sand, water, plant tissue, and fish food to understand nutrient cycling and uptake within the system. They emphasized the role of microbial communities in the sand beds, responsible for converting fish waste into plant-usable forms.

This detailed analysis reveals the intricate biological interactions that contribute to the system’s success. The findings pave the way for further research and development, exploring optimization strategies to enhance productivity and address potential nutrient limitations, while ensuring its adaptability to diverse environments and resource constraints.

Research Focus and Results in ‘The efficiency of Water Use of an Integrated Fish/Vegetable Co-Culture System’.

The study’s authors had two primary objectives in conducting this research on an IAVS, firstly, they sought to implement an IAVS that operated with high efficiency of water use and minimal chemical, technological, and labor inputs. They highlight the significance of expanding plant growth capacity relative to fish rearing capacity.

This increased ratio allows the vegetable crops to effectively recover nutrients from the fish waste, leading to suitable water quality and good fish production without the need for extensive water exchange or sophisticated biofiltration equipment. The system tested in this study kept solid waste within sand beds, allowing for good crop growth without the need for supplemental fertilizers (McMurtry 1997a).

Secondly, the study investigated how varying component ratios within the IAVS influence fish versus vegetable productivity. The researchers specifically examined the effects of four different ratios of biofilter volume (BFV) to fish rearing tank volume on water use efficiency, protein and calorie production, and the economic viability of the system. This involved analyzing the trade-offs between fish and vegetable production under different biofilter configurations, aiming to understand how to optimize either fish or vegetable output while preserving the system’s overall functional balance (McMurtry 1997a)

The authors highlight the importance of sand composition to prevent clogging and maintain optimal system performance. They also provide a detailed breakdown of the sand particle size distribution, emphasizing the predominance of medium to coarse sand particles which likely contributes to good drainage and aeration within the biofilter (McMurtry 1997a).

.The key results of the study can be summarized as follows:

Water Use:

The amount of replacement water needed for evapotranspiration and leakage increased with higher BFV/tank ratios.
Daily water exchange rates remained low, ranging from 1.2% to 4.7% of the system’s capacity.
The study achieved a water use efficiency of 24.1 g of food production per liter of water, marking a significant improvement over traditional aquaculture and agriculture methods.

Production:

In Experiment 1, both fish and tomato production increased with larger BFV/tank ratios. However, tomato yield per unit area decreased with increasing biofilter size, suggesting possible nutrient limitations.
In Experiment 2, fish production wasn’t significantly affected by BFV/tank ratios, while tomato yield continued to increase with larger biofilters.
The researchers observed good fish growth rates without complex filtration, comparing favorably with other recirculating systems.
Tomato yields achieved in the study fell within the range reported for other temperate zone recirculating systems.

Water Use Efficiency:

In both experiments, fish production per liter of water used decreased with increasing BFV/tank ratios.
Tomato fruit yield per liter of water, on the other hand, tended to increase with larger biofilters.
Overall, total energy production efficiency didn’t show a significant response to biofilter size.
Total protein production per liter of water decreased as BFV/tank ratio increased, mainly due to the larger contribution of fish protein.

Deep sampling of the sand substrate resulted in the development of leaks in the plastic liners which became obvious as replacement water volume increased over time. The biofilter liners would probably be sufficient for normal operating procedures but did not hold up to the rigors of experimental sampling of the sand medium (McMurtry 1997a).

Economic Returns:

Projected annual tilapia yields and corresponding economic returns increased with larger BFV/tank ratios.
Projected tomato yields per unit area and economic returns, however, decreased with increasing biofilter size.
Despite being experimental, the IAVS demonstrated gross returns comparable to traditional commercial greenhouse tomato production.

Fish Feed

The researchers intentionally omitted the vitamin and trace element package that is typically included in commercial fish feeds. This decision was made to prevent the buildup of trace elements in the system’s water, which could potentially reach toxic levels. The fish were fed twice daily, at 0800 and 1300 hours. The initial daily feeding rate was set as a percentage of the fish biomass and was subsequently adjusted upwards throughout the experiment based on the observed feeding response of the fish. The paper notes that the feed was fully consumed by the fish within 15 minutes of each feeding, indicating healthy appetites and efficient feed utilization. In addition to the provided feed, the tilapia also grazed on algae (Oscillatoria spp. and Ulothrix spp.) that grew naturally in the fish tanks and on the tank sides. This supplemental grazing likely contributed to the fish’s overall nutrient intake.(McMurtry 1997a).

Clogging as a potential problem

The paper acknowledges that clogging can be a common issue in biofilters, especially in traditional designs where water flow is constant and unidirectional. Clogging can disrupt the essential processes of water filtration and nutrient breakdown by inhibiting the flow of water and oxygen through the sand bed, hindering the activity of beneficial bacteria, and potentially leading to the buildup of harmful substances in the water.

The Reciprocating Biofilter as a Solution:

To prevent clogging and maintain efficient biofiltration, the researchers implemented a unique “reciprocating biofilter” design. This design involves alternating phases of flooding and draining the sand bed. The draining phase allows air to penetrate the sand bed, replenishing oxygen levels essential for the beneficial bacteria that break down waste and convert nutrients. The paper also highlights the importance of using the right type of sand in the biofilter to prevent clogging. The researchers used a specific type of builder’s grade sand with a carefully chosen particle size distribution to ensure good drainage and prevent compaction. The paper suggests that the reciprocating biofilter design, combined with the appropriate sand composition, was successful in preventing clogging and maintaining efficient water filtration throughout the experiments (McMurtry 1997a).

Conclusions:

The IAVS successfully achieved its objectives of high water use efficiency and simplified operation, eliminating the need for significant water exchange or complex biofiltration.
The study demonstrates that manipulating the BFV/tank ratio can shift the balance between fish and vegetable production, highlighting the flexibility of the system.
Further research is recommended to optimize production for either fish or vegetables while maintaining the system’s functional balance.

The study found that both fruit production per liter of water and the number of crop applications per liter of water increased with larger biofilter sizes. This suggests that larger biofilters provide more space for plant growth and nutrient uptake, leading to more efficient water utilization for vegetable production.

The observation that tomato yield per square meter of biofilter declined with increasing BFV suggests a potential nutrient limitation with larger biofilters. The sources speculate that the increased ratio of plant growth capacity to fish rearing capacity might lead to insufficient nutrients for optimal vegetable growth in larger biofilters.

The study emphasizes that these yields, while promising, should be considered within the context of the experimental setup. Factors like leaks in the biofilter liners during Experiment 2 and unusually high temperatures impacting fruit set in Experiment 1 may have influenced the overall productivity.

The authors note that the yields achieved, particularly for tomatoes, fall within the range observed in other recirculating aquaculture systems operating in temperate zones. They also highlight the system’s remarkable water use efficiency, producing 24.1 g of food per liter of water in Experiment 1, a figure significantly higher than many conventional food production methods. This efficiency underscores the potential of IAVS for sustainable and resource-conserving food production, especially in regions facing water scarcity.

Optimizing for Fish Production:

Smaller biofilters could lead to higher fish production per liter of water: While larger biofilters might benefit vegetable production, the study observed that fish production per liter of water was higher with smaller BFV/tank ratios. This indicates that, in terms of water use efficiency for fish, a smaller biofilter might be more advantageous.
Larger rearing tanks and higher stocking densities might also enhance fish production: The sources suggest that to maximize protein production per unit volume of water, using a smaller BFV, a larger rearing tank, or increasing the fish stocking density could be beneficial. This implies that focusing on the fish component of the system, with adjustments to tank size and stocking density, could improve overall fish output.

Balancing Fish and Vegetable Production:

The “optimum” ratio is context-dependent: The sources conclude that the ideal BFV/tank ratio for an IAVS is not fixed but depends on specific regional conditions, market demands, and desired production goals.

Trade-offs exist: The study highlights that trade-offs exist between maximizing fish and vegetable production. A larger biofilter might support greater vegetable yields but could lead to lower fish production per liter of water. Conversely, a smaller biofilter could optimize water use for fish production but potentially limit vegetable yields.
Flexibility is key: The ability to adjust the BFV/tank ratio allows the system to be tailored to prioritize either fish or vegetable production, depending on local needs and market trends. This flexibility is a crucial advantage of the IAVS, enabling it to adapt to different circumstances and maximize resource utilization for the desired output.

Research Focus and Results in ‘Effects of Biofilter/Culture Tank Volume Ratios on Productivity of a Recirculating Fish/Vegetable Co-Culture System’

The main reason for the study presented in the source was to evaluate the effects of different biofilter volume (BFV) to culture tank volume ratios on the performance of the iAVs system. This study investigated the yields of tilapia and two types of vegetables, tomatoes and cucumbers, in an iAVs system. The researchers conducted three separate experiments, each focusing on different aspects of the system’s performance and using different BFV/tank ratios.

The researchers aimed to understand how these ratios influenced:

Fish and crop growth: Researchers assessed the growth rates, yields, and overall productivity of both fish and vegetable components of the system across various BFV/tank ratios.
Water quality: The study measured parameters like dissolved oxygen, temperature, pH, and the concentrations of ammonia (TAN), nitrite, and nitrate to determine the impact of BFV/tank ratios on water quality.
Nutrient levels: Researchers analyzed nutrient concentrations in the irrigation water and sand beds to assess the efficiency of nutrient utilization and potential imbalances.
Clogging and channeling in the biofilter: The study investigated whether different ratios affected the occurrence of clogging and channeling, which can impact the biofilter’s performance.

The study’s ultimate goal was to determine the optimal BFV/tank ratio for a balanced and efficient iAVs system. This involved identifying the ratio that would:

Support healthy fish growth and maximize fish production.
Provide sufficient nutrients for vigorous vegetable growth and high yields.
Maintain excellent water quality without relying heavily on water exchange.
Minimize the need for external inputs like lime and chemical fertilizers.
Ensure the long-term functionality and stability of the system, including the prevention of clogging in the biofilter.

The researchers conducted three experiments over a year, using different fish species and vegetable crops. They measured various parameters, including:

Fish growth rates, yields, and overall productivity.
Vegetable yields and growth characteristics
Water quality parameters (dissolved oxygen, temperature, pH, ammonia, nitrite, nitrate levels)
Nutrient concentrations in the irrigation water and sand beds
Occurrence of clogging or channeling in the biofilter

Results

Increasing the BFV/tank ratio generally led to improved water quality, with lower concentrations of ammonia (TAN) and nitrite, higher dissolved oxygen levels, and more stable pH.
Fish growth rates and overall productivity tended to increase with larger BFV/tank ratios, reflecting the positive effects of improved water quality.
Vegetable yields per plant decreased with increasing BFV/tank ratio, but the total yield per plot (biofilter) increased, indicating more efficient nutrient utilization with larger biofilters.
Nutrient concentrations in the irrigation water were generally low, suggesting effective nutrient uptake by the plants. However, some imbalances were observed, particularly low potassium levels, which might require adjustments for optimal plant growth.
No clogging or channeling was observed in the biofilters throughout the experiments, even after three years of continuous operation. This highlights the system’s effectiveness in preventing clogging, a common issue in traditional recirculating aquaculture systems.

Here are the key points from the source regarding clogging:

The study specifically aimed to design a system that would minimize clogging, a common issue in traditional recirculating aquaculture systems.
The researchers carefully selected a sand medium composition (99.25% quartz sand and 0.75% clay) and particle size distribution to optimize drainage and prevent clogging.
Throughout the experiments, there was no noticeable change in the wastewater percolation rate through the sand beds, indicating the absence of clogging.
No evidence of channeling, which can also lead to localized anaerobic conditions and reduced biofilter efficiency, was observed.
Analysis of sand samples collected at the end of the study showed low organic content, further supporting the conclusion that clogging did not occur.

Water Use

The researchers highlight that the iAVs system demonstrated excellent water conservation. Over the course of the year-long study, the average daily water use was 2.8% of the total system water volume. This water usage primarily accounted for evapotranspiration and leakage losses.

The researchers emphasize that using a more durable material for the fish tanks could potentially eliminate or reduce leakage, further improving the system’s water efficiency.

Oxygen

The researchers aimed to design a system that provided sufficient oxygen to the biofilters to support efficient microbial conversion of ammonia to nitrate. They highlight that previous recirculating aquaculture systems often faced challenges in maintaining adequate oxygen levels in the biofilters, which could hinder nitrification and lead to the buildup of toxic ammonia.

Reciprocating Flow and Aeration: The iAVs system utilized a reciprocating flow mechanism to irrigate the biofilters. Water was pumped from the fish tanks to the surface of the sand beds, flooding the biofilter surfaces and then draining back into the tanks. This alternating flooding and draining process, combined with the cascading effect of the returning water, enhanced oxygenation in the biofilters.
Dissolved Oxygen Measurement: The researchers monitored dissolved oxygen levels in the fish tanks, taking measurements at least weekly. They observed that dissolved oxygen concentrations generally ranged from 4.8 to 7.8 mg/L, with minimal day-to-day variation.
Oxygen and Biofilter/Tank Ratio: The study found a positive correlation between the biofilter/culture tank volume ratio and dissolved oxygen concentrations. Systems with larger biofilter volumes tended to have higher dissolved oxygen levels.
Nighttime Filtration and Oxygen: Although the study didn’t implement nighttime filtration, the authors suggest that further filtration at night might improve water quality as stocking density and volume are increased. This suggestion implies that increased oxygen demand from higher fish populations in larger tanks could be addressed by extending filtration processes into the nighttime hours.

Optimization

While the study successfully demonstrated the positive impacts of larger BFV/tank ratios on the iAVs system, the authors acknowledge that further optimization is necessary to achieve maximum efficiency and productivity.

Here are some key areas for optimization identified in the research:

Intensifying Production: The researchers aimed to understand the effects of component ratios on system performance rather than pushing the limits of production. The upper limit of fish stocking density and its relationship to plant carrying capacity were not determined. Future studies could explore higher stocking densities in conjunction with larger culture tanks to potentially increase fish production rates without compromising water quality. This, in turn, could lead to higher nutrient availability for the plants and potentially increase vegetable yields.
Enhanced Filtration: The authors suggest that further filtration at night could be beneficial if stocking density and tank volume are increased. This statement implies that nighttime filtration may help to maintain optimal water quality even with higher fish populations and larger tanks.

Research Focus and Results in ‘Mineral nutrient concentration and uptake of tomato irrigated with recirculating aquaculture water as influenced by the quantity of fish waste products supplied’.

The research in this paper focused on determining the mineral nutrient concentration, balance, and accumulation in tomato plants grown in sand biofilters irrigated with aquaculture wastewater. The researchers wanted to investigate the feasibility of using fish waste as a sustainable nutrient source for tomato production in an integrated aquaculture-vegetable system (iAVs). The study focused on growing two different cultivars of tomatoes, ‘Laura’ and ‘Kewalo’, in sand biofilters irrigated with water from tanks containing tilapia.

The researchers examined how varying the ratio of fish tank to biofilter size impacts nutrient levels in tomatoes grown using the fish waste as fertilizer. Their findings show that this integrated system can successfully produce both fish and tomatoes, although adjustments to fish feed composition are suggested to optimize plant nutrient uptake. Specifically, they recommend altering the levels of several minerals in the fish feed to improve the overall system efficiency and plant yields. The study details the methods used, the results obtained from two experiments, and a discussion of the implications for optimizing integrated aquaculture-olericulture systems.

Ammonium

Ammonium (NH4+) is a key nutrient in integrated aquaculture-vegetable systems (iAVs). The sources explain that much of the ammoniacal-N from fish waste in the aquaculture water wasn’t oxidized before being used to irrigate the biofilter. This means the tomatoes could absorb the ammonium. This differs from other systems where the ammonium is oxidized before irrigating the plants. The presence of both ammonium and nitrate ions (NO3-) is thought to be one of the reasons the tomatoes produced a good yield, as this combination leads to optimal growth and protein production in most plants.

The availability of ammonium at low concentrations may also stimulate nitrate reduction, further boosting plant growth and yield. This is because nitrate reduction in plants requires energy, and if the plant can absorb ammonium directly, it conserves energy that can be used for other processes like growth (McMurtry 1993a).

The researchers also suggest that tomatoes in iAVs may be able to directly utilize organic nitrogen in the form of amino acids, in addition to inorganic nitrogen sources like ammonium and nitrate.

While the study didn’t directly measure amino acid uptake, they cite previous research by Ghosh and Burris (1950) which found that tomatoes can utilize certain amino acids, including alanine, glutamic acid, histidine, and leucine, just as effectively as inorganic nitrogen sources.

This finding suggests that the availability of amino acids in the fish waste could be another factor contributing to the successful growth of tomatoes in iAVs.

The researchers did not analyze the fish waste for amino acid content, so it is unclear which specific amino acids were present and in what quantities. Further research would be needed to determine the extent to which amino acid uptake contributes to tomato nutrition in iAVs.

Nitrate (NO3-) is an important source of nitrogen for plants in integrated aquaculture-vegetable systems (iAVs), but it’s not the only one. While nitrate is often considered the primary nitrogen source for plants, the paper emphasizes that the availability of both ammonium (NH4+) and nitrate is beneficial for plant growth. The researchers found that the iAVs in their study maintained nitrate levels within acceptable limits for tilapia, and the tomatoes were likely able to utilize both forms of nitrogen.

The paper also notes that the form of nitrogen absorbed by plants can significantly influence their growth, ion balance, and the composition of their metabolic products.

Here’s a breakdown of how nitrate is involved in the iAVs system, according to the sources:

Source of Nitrogen: Nitrate is one of the main forms of nitrogen available to plants in iAVs. It’s produced through the breakdown of organic matter in the fish waste.
Stimulates Cation Uptake: The uptake of nitrate by plants stimulates the uptake and translocation of cations (positively charged ions) as counter-ions to maintain electrical balance within the plant cells. This can lead to higher concentrations of cations like potassium, calcium, and magnesium in plant tissues.
Organic Anion Synthesis: After nitrate is absorbed and reduced within the plant, organic anions (negatively charged ions) accumulate to balance the positive charge of the cations. This balance is important for plant metabolism and growth.
Potential for Imbalances: While nitrate is essential, relying solely on nitrate nutrition can lead to excess uptake of certain cations, potentially resulting in nutrient imbalances. This is why the presence of ammonium, which doesn’t have the same effect on cation uptake, can be beneficial.

Overall Nutrient Sufficiency:

The tomato plants in both experiments generally absorbed nutrients from the fish waste at levels exceeding deficiency thresholds. This indicates that fish waste can serve as a viable source of essential nutrients for tomato growth. However, the study revealed some imbalances that need to be addressed for optimal plant nutrition:

Calcium Deficiency: Calcium levels were consistently low when fish waste was the sole nutrient source. The researchers suggested increasing the calcium content in fish feed to address this issue.
Excess Sulfur: Sulfur levels were consistently high. The researchers proposed reducing the sulfur content in fish feed as a potential solution.
Micronutrient Uptake: Micronutrient levels in plant tissues were higher than typical sufficiency recommendations, yet no toxicity symptoms were observed. This excess uptake might be linked to the high nitrate levels, which can stimulate the absorption and accumulation of cations.

Impact of Fish Biomass and Feed Rate:

The study highlighted the relationship between fish biomass, feed input, and nutrient availability for the plants:

Sufficient Nutrient Supply: The metabolic by-products generated per kilogram increase in fish biomass were sufficient to sustain two tomato plants for three months. This suggests a direct link between fish growth and nutrient availability for the plants.
Potassium Limitation: Under conditions of reduced fish growth rates (and consequently, lower feed input), potassium became a limiting factor for tomato growth. This underscores the importance of maintaining adequate fish stocking densities and feeding rates in iAVs to ensure sufficient nutrient supply for the plants.

Optimization

The research in this paper highlights the potential of integrated aquaculture-vegetable systems (iAVs), but also emphasizes the need for optimization to achieve the best results. The main areas for optimization identified in the study are:

Fish Feed Composition: The study found that the standard fish feed used in the experiments did not perfectly match the nutritional needs of the tomato plants. This led to deficiencies in calcium and excesses in sulfur. The researchers suggest modifying the fish feed to better align with the plant requirements by:
- Increasing nitrogen and calcium.
- Reducing phosphorus, potassium, sulfur, iron, manganese, copper, and zinc.

Fish Biomass and Feed Rate: Maintaining appropriate fish biomass and feed rates is crucial to ensure a consistent supply of nutrients to the plants. The study demonstrated that each kilogram increase in fish biomass provided sufficient nutrients for two tomato plants for three months. However, when fish growth rates were reduced, potassium became a limiting nutrient. This suggests that:
- Stocking densities and feeding rates should be carefully managed.
- The optimal ratio of fish biomass to plant density needs to be determined for specific combinations of fish and vegetable species.

Research Focus and Results in ‘Yield of Tomato Irrigated with Recirculating Aquaculture Water as Influenced by Quantity of Fish Waste Products Supplied’

The research paper focused on investigating the relationship between tomato yield and the volume of the biofilter in an integrated aquaculture-olericulture system (iAVs). The researchers were particularly interested in how biofilter volume influences the efficiency of nutrient extraction from aquaculture water and the overall productivity of the system.

To explore this, they conducted two experiments using different tomato cultivars (‘Laura’ and ‘Kewalo’). In both experiments, they varied the ratio of fish tank volume to biofilter volume (BFV), effectively changing the number of tomato plants per unit of fish biomass or feed input.

This study focused on determining the optimal ratio between fish tank volume and biofilter volume (BFV) to maximize tomato yield.

The researchers found that:

Fruit yield per biofilter increased with increasing BFV. This suggests that a larger biofilter allows for more efficient nutrient extraction from the fish effluent, leading to higher plant yields.
Yield per plant declined with increasing BFV, indicating that nutrient availability per plant was greater with smaller biofilters.

Optimization

While larger biofilters yielded more tomatoes overall, the study emphasizes the need to optimize the ratio between feed input, fish biomass, water volume, and biofilter volume for specific fish and vegetable combinations. This optimization would likely involve balancing total yield with yield per plant, considering factors like nutrient availability, plant competition, and economic efficiency (McMurtry 1993b).

Research Focus and Results in ‘Mineral Content and Yield of Bush Bean Cucumber Tomato Cultivated in Sand Irrigated with Recirculating Aquaculture Water’.

The study examines the growth of tilapia and various vegetable crops in a closed system where fish waste fertilizes the plants, and the plants filter the water. A variety of vegetables can be grown in the system. This study focused on bush beans, cucumbers, and tomatoes. Researchers measured crop yields, fish biomass, and nutrient levels in both the water and the growing medium. The results indicate that this integrated system can produce significant yields of both fish and vegetables while conserving resources and potentially reducing costs compared to traditional methods. Challenges like heat stress and disease were encountered and discussed.

Cascade Aeration:

The return water from the sand beds discharged into the fish tank at a height of 0.5 meters above the water level, creating a cascade effect that helps aerate the water. This aeration is essential for maintaining adequate dissolved oxygen levels for the fish.

Ammonia Toxicity:

The paper explains that maintaining a pH below 7.0 is crucial for preventing ammonia toxicity to fish. “The pH remained below 7.0 such that virtually all of the ammonia remained in ionized form (non-toxic to fish), and plant assimilation of nitrogenous compounds maintained nitrite concentrations below tolerance limits”.

PH:

The paper explains that the oxidation of ammonia to nitrate (nitrification) by microbes in the sand beds can lower the pH (make it more acidic). “In other fish rearing systems, periodic additions of a base are necessary to stabilize pH because the nitrification process is acidifying”.

Buffering Capacity of the Sand Beds: The iAVs system, however, doesn’t require alkaline amendments due to the buffering capacity of the sand beds. The accumulation of organic matter in the sand, particularly near the furrows, helps maintain a stable pH. “Alkaline amendment was not necessary in this system because of two factors: a) nitrification took place in the sand beds where organic matter accumulated to provide buffering capacity, and b) N was provided in both ammonical and nitrate form”.
Plant Uptake and pH: The paper further explains that plant uptake of nitrate ions can help stabilize pH by releasing hydroxide ions, which counteract acidity. “Ammonical-N and nitrite in the fish excrement is rapidly converted to nitrate by microbes, and the nitrate ions are absorbed by the root cells and exchanged for hydroxide ions (or bicarbonate ions produced during respiration)”

Sterilization Considerations:

While the study did not initially sterilize the sand, the unintentional introduction of a bacterial pathogen highlighted the importance of sterilization in preventing disease outbreaks. Future applications of IAVS should consider sterilization methods to ensure optimal plant health and prevent potential yield losses. The presence of pathogens in the sand can vary depending on the source and previous land use. For instance, if the sand was previously used for tobacco cultivation, known to be susceptible to Pseudomonas solanacearum, sterilization would be crucial to prevent disease outbreaks in subsequent crops.While sterilization may not be necessary in small-scale systems using sand from a known, pathogen-free source, it becomes a significant factor in commercial settings. Large-scale operations often source sand from various locations, increasing the risk of introducing pathogens.

The mean values of P, K, Mn, and CEC by sampling region. P, K, and Mn concentrations were greatest nearest the furrow and at the surface”. This statement directly indicates a higher concentration of these nutrients near the furrow. The paper also mentions that “nutrient levels in the 0-160 mm profile within 50 mm of the irrigation furrow did show a substantial increase”. This observation confirms that the area closest to the furrow received a higher concentration of nutrients compared to other areas of the sand bed.

This nutrient gradient makes nutrients more accessible to plant roots;

The localized application of nutrient-rich water through furrows creates a higher concentration of nutrients in the root zone.
Plants generally absorb nutrients through their roots.
Therefore, a higher concentration of nutrients near the roots makes those nutrients more readily available for uptake.

Cation Exchange

Cation exchange capacity (CEC) is a fundamental property of soil and other growing media that significantly influences nutrient availability for plants. CEC refers to the ability of a soil to hold and exchange positively charged ions (cations), such as essential plant nutrients like calcium (Ca2+), magnesium (Mg2+), potassium (K+), and ammonium (NH4+).

The paper states, “CEC changes tended to be greatest near furrows because of accumulation of organic matter on the surface.” This statement highlights that higher CEC values are observed in areas where organic matter accumulates, indicating a greater capacity to retain nutrients. The accumulation of organic matter from fish effluent near the furrows leads to higher CEC in those areas. This finding is consistent with the general principle that organic matter decomposition improves a soil’s ability to hold and exchange nutrients. A higher CEC in the sand medium ensures that these nutrients are retained within the root zone, preventing them from leaching away and becoming unavailable to the plants. This retention mechanism contributes to the system’s efficiency in recycling nutrients and supporting plant growth.

Research Focus and Results in ‘Performance of an Integrated Aquaculture-Olericulture System as influenced by component ratio’.

The focus of this study was to evaluate the influence of the ratio between fish tank volume and biofilter volume (BFV) on fish growth rate and water quality in an integrated aquaculture-olericulture system (iAVs). Researchers wanted to understand how different tank-to-biofilter ratios would affect the overall performance of the iAVs system, taking into account:

Fish growth rate
Water quality parameters, including dissolved oxygen, temperature, and nitrogenous compounds
The need for pH adjustments and amendments

The researchers conducted three experiments using different plant species (tomato and cucumber) and varying the BFV ratios to assess their impact on the system’s efficiency and productivity. The study aimed to determine the optimal BFV ratio that would maximize both fish and vegetable yields while maintaining suitable water quality conditions for fish growth.

Before planting, the sand was fumigated with methyl bromide-chloropicrin to prevent infection from soil-borne bacterial pathogens. Each biofilter was then inoculated with a suspension of Nitrosomonas and Nitrobacter species to promote nitrification. The researchers fumigated the sand with methyl bromide-chloropicrin to prevent infection from soil-borne bacterial pathogens. Specifically, they were concerned about the soil-borne bacterial pathogen Pseudomonas solanacearum, which causes bacterial wilt in plants. Previous studies indicated a risk of infection from this pathogen, prompting the pre-plant fumigation.

The researchers took this step to ensure the health and successful growth of the tomato and cucumber plants used in the experiments.

The researchers inoculated each biofilter with a suspension of these bacteria to jump-start the nitrification process

pH:

The paper states that water pH rapidly declines when the system is operated without plants because inputs of nitrogen from the fish feed exceed the rate of nitrification in the biofilter, leading to acidification of the water. When plants grow normally in the system, their uptake of nitrogen helps to maintain a stable pH. Nitrate uptake by plants occurs in exchange for hydroxide or bicarbonate ions, which increases the alkalinity of the growing medium. The paper also suggests that ammonia can react with hydroxide ions released during plant anion adsorption to buffer nutrient solution pH. Therefore, plant growth plays a crucial role in stabilizing water pH in an iAVs system, preventing excessive acidification. Without plants, the system requires regular additions of alkaline amendments to maintain a suitable pH for fish.

Research Focus and Results in ‘Food Value Water Use Efficiency Economic Productivity Integrated Aquaculture-Olericulture System Component Ratio.’

This research paper investigates the efficiency of an integrated aquaculture-olericulture system, combining fish farming with vegetable cultivation in a recirculating water system. The study examines the effects of varying biofilter-to-tank volume ratios on fish and vegetable yields, water use efficiency, and overall economic productivity. Experiments using tilapia and tomatoes (and one using cucumbers) measured caloric and protein production, analyzing how different ratios impact nutrient uptake, water quality, and ultimately profitability. The results indicate a trade-off between maximizing fish production and optimizing vegetable yields, depending on the chosen biofilter-to-tank ratio.

Conclusion

The history of IAVS presents a compelling case study in the evolution of sustainable food production methods. While IAVS emerged as a pioneering system backed by rigorous scientific research, its journey has been marked by both triumphs and setbacks. Dr. McMurtry’s vision of a simple, efficient, and accessible system, capable of addressing global food security challenges, materialized through meticulous research and development. The numerous benefits of IAVS, including its water and nutrient efficiency, low-tech requirements, and ability to produce both high-quality protein and vegetables, make it an ideal solution for diverse environments and resource constraints.

However, the story of IAVS also highlights the complexities of disseminating innovation and ensuring its integrity. Factors like the Speraneos’ modifications, the rapid rise of the internet, and a lack of thorough research in the broader aquaponics community have contributed to the overshadowing of IAVS by less efficient systems. The confusion caused by inaccurate terminology and the uncritical adoption of online information have further compounded this issue, leading to a situation where the industry is, in many ways, “reinventing the wheel,” grappling with challenges that IAVS effectively addressed decades ago.

Despite these challenges, the legacy of IAVS remains a beacon of hope for sustainable food production. Its scientific foundation, robust design, and proven efficacy offer valuable insights for researchers and practitioners alike. A renewed focus on IAVS, informed by thorough literature reviews, adherence to the scientific method, and the adoption of proper nomenclature, is crucial for advancing the field of aquaponics towards a truly sustainable and impactful future.

By learning from the past and embracing the principles of IAVS, the aquaponics industry can move towards a future based on sound scientific principles and the efficient use of resources, ultimately contributing to a more sustainable and productive food production system.

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