An Open Letter Regarding the Representation of iAVs in Recent Saltwater Integrated Fish and Plant Culture Research

May 3rd 2025

To: Dr. Abdul Jaleel (1.2), Radhakrishnan Subramanian (2), Chythra Somanathan Nair, Ramya Manoharan (2), Drishya Nishanth (1.2) (Authors of Animals 2025, 15, 1246)
Cc: The Editorial Board of Animals, The iAVs Community

¹ASPIRE Research Institute for Food Security in the Drylands (ARIFSID), United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates

²Department of Integrative Agriculture, College of Agriculture and Veterinary Medicine, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates

We are dedicated to the accurate dissemination of information regarding the Integrated Aqua-Vegeculture System (iAVs). It is in this spirit that we address the recent publication: Integrating Desert Sand Utilization in Saltwater Aqua-Vegeculture Production: Performance Evaluation of Yield and Biochemical Composition. Animals 2025, 15, 1246. https://doi.org/10.3390/ani15091246

We acknowledge and commend the exploration of integrated fish and plant culture systems as this is a vital area of research for sustainable food production. However, we feel compelled to express significant concerns regarding specific aspects of the paper, namely the representation and implementation of the iAVs methodology.

This is not the first instance where we have observed a conflation between iAVs and Sandponics (SP) potentially stemming from related research initiatives. We previously attempted to address similar points privately, offering resources to clarify the distinct principles and foundational research of iAVs, but did not receive a response (see links to previous correspondence below). The recurrence of these fundamental discrepancies in a peer-reviewed publication necessitates this public clarification to ensure accuracy within the scientific record and for the benefit of researchers and practitioners in the field.

While the paper cites some foundational iAVs work (McMurtry et al.), it appears to conflate iAVs with Sandponics. This is evident in the statement: “SP faces several challenges, including the requirement for specialized operator training, potential nutrient deficiencies in crops…” which implicitly attributes these Sandponics-specific challenges to the system described as iAVs in the study.

For clarity:

• iAVs (Integrated Aqua-Vegeculture System): Developed by Dr. Mark McMurtry et al., iAVs is specifically designed for operational simplicity, minimizing the need for specialized training. Its core principle involves robust nutrient cycling through the mineralization of all fish waste (including solids/sludge) within the sand biofilter, inherently designed to prevent systemic nutrient deficiencies. It is a distinct integrated aquaculture and horticulture system with specific design criteria. (See: https://iAVs.info/the-kiss-principle-in-iAVs/)
• Sandponics (SP): This term refers to different approaches using sand media, in a hydroponic system using inorganic fertilizers instead of fish, which presents different operational complexities. (See: https://iAVs.info/sandponics-is-not-iAVs/)

Attributing potential SP challenges (like specialized training needs or inherent nutrient deficiencies) to iAVs is inaccurate. Furthermore, the citation used [Ref 11: Kimera et al., 2023] to support the claim of “potential nutrient shortages” in iAVs appears problematic. That paper itself seems to misinterpret certain iAVs principles and relies heavily on Sandponics literature. Citing a study that itself may misapply iAVs principles to support a characterization inconsistent with iAVs design philosophy is potentially misleading. (We note that we have also attempted to contact the authors of the Kimera paper regarding these points without response).

Additionally, the Kimera paper states, “channeling fish effluents (organic fertilizer) to the sand grow beds can support the growth of kale under our experimental conditions without any requirements for supplemental fertilization,” which contradicts the notion of inherent nutrient deficiencies attributed to iAVs in your paper. Similarly, Kimera et al. describe such systems as “easily monitored and controlled,” contrasting with the claim regarding “specialized training.”

The methodology described and depicted in the paper deviates substantially from established iAVs principles, raising questions about whether the system tested accurately represents an iAVs:

• Separate Biofilter: Figure 1 illustrates a “Biofilter tank & Media” separate from the plant grow beds. This contradicts a fundamental iAVs design principle, where the sand grow bed itself serves as the sole integrated mechanical and biological filter. A separate biofilter unit is not part of the standard iAVs configuration.
• Incorrect Tank/Bed Design & Media: The diagrams lack characteristic iAVs features like a catenary-bottom fish tank (for passive solids concentration) and a sloped grow bed floor (for complete drainage). Figure 1 depicts a level biofilter, whereas McMurtry specifies a slope (e.g., 1/200) for drainage.
• The use of gravel layers beneath the sand in the plant culture troughs deviates from standard iAVs sand bed construction, which utilizes specific sand compositions and no gravel (as detailed in McMurtry’s work regarding percentages of quartz sand, clay/silt, etc., which are not detailed for the desert sand used here). Gravel significantly reduces the surface area crucial for mineralization processes central to iAVs.
• Water Circulation: Figure 1 shows water overflowing from the top of the fish tank and a pump only in the sump. Standard iAVs design, as described by McMurtry, involves pumping water from the bottom of the fish tank to transport settled solids to the sand beds for mineralization.
• Daily Sludge Removal: Section 2.6 states, “Sludge was collected daily by siphoning method, and any floating sludge was removed.” This practice is directly contrary to the core operational principle of iAVs. iAVs relies fundamentally on the retention and mineralization of fish solids on the surface of the sand biofilter to provide nutrition to the plants. McMurtry explicitly states, “the sand beds served not only as biofilters and substrate for vegetable crops but also as a location for decomposition of waste solids,” and notes that removing solids, as done in some other systems, “sequestered nutrients… making them unavailable to plants.” Daily removal of solids fundamentally disrupts this integrated nutrient cycle, effectively preventing the system from functioning as an iAVs and invalidating the assessment of “iAVs performance” under these conditions.
• Irrigation Schedule: While McMurtry provides detailed irrigation parameters, this paper lacks specifics on frequency, duration, timing (day/night), and volume per cycle, making replication and comparison difficult.

Given these significant deviations – the conflation with SP characteristics and the implementation of methods (especially daily solids removal) that contradict core iAVs principles – the system described and tested does not function as a standard iAVs. Consequently, the results presented and the conclusions drawn regarding “iAVs performance,” nutrient cycling, and suitability do not accurately reflect the potential or behavior of a correctly implemented iAVs.

For the advancement of scientific understanding in integrated food production systems, precise terminology and adherence to established methodologies are crucial. We urge the authors and the journal Animals to review and address these significant discrepancies between the system described in the paper and the established principles and practices of the Integrated Aqua-Vegeculture System (iAVs).

Conflating distinct systems like iAVs and Sandponics, and evaluating performance based on a methodology that fundamentally alters the system’s core nutrient cycling mechanism, can unfortunately misinform the scientific community and hinder progress in optimizing these valuable technologies.

We trust that this clarification is received in the spirit of constructive scientific discourse. We remain hopeful that future research in this important area will more closely align with the specific designs and operational principles of the systems being investigated, allowing for a more accurate assessment of their true potential.

Sincerely,

Rita T. Pryce

Additional Information:

• iAVs Simplicity (KISS Principle): https://iAVs.info/the-kiss-principle-in-iAVs/
• iAVs vs. Sandponics: https://iAVs.info/sandponics-is-not-iAVs/
• Sand vs. Gravel Media: https://iAVs.info/sand-versus-gravel-as-biofilter-media/
• Scientific Method & Literature Review: https://iAVs.info/the-scientific-method/

Previous Correspondence:

• Letter sent to Dr. Abdul Jaleel (Jan 3, 2025): https://iAVs.info/wp-content/uploads/2025/05/letter-to-abdul-jaleel-jan-3-2025-1.pdf
• Letter sent to Dr. Abdul Jaleel (Dec 11, 2024): https://iAVs.info/wp-content/uploads/2025/05/letter-to-abdul-jaleel-dec-11-2024.pdf
• Notification of this post sent to all authors (May 3, 2025): https://iAVs.info/wp-content/uploads/2025/05/letter-to-abdul-jaleel-and-authors.pdf

Useful Citations from the paper:

• The iAVs design requires minimal or no electric power to operate, making it ideal for sustainable farming (Wang 2024).
• The sand filter bed component of the iAVs is considered ideal for vegetation growth because its pH and water permeability are similar to those of soil (Wang 2024).
• The sand filter bed provides sufficient concentrations of potassium, calcium, and iron, nutrients often lacking during vegetation growth (Wang 2024).
• The sand filter bed efficiently utilizes organic waste from fish without requiring mechanical means of water filtration for sedimentation, nitrification, and nitrate mineralization (Wang 2024).
• Studies conducted in Raleigh, North Carolina, linked to the iAVs description, showed that aquaponics (implied for systems like iAVs and NCSU) can yield more than 50 kg of tilapia per year per cubic meter of water, in addition to approximately 360 kg of tomatoes or other fruits and vegetables (Wang 2024).
• As a media-filled bed unit, the iAVs is capable of growing most plant types (Wang 2024).
• iAVs systems (as media-filled bed units) have a simple design (Wang 2024).
• iAVs systems (as media-filled bed units) have a high fault tolerance rate (Wang 2024).
• iAVs systems (as media-filled bed units) have low energy consumption (Wang 2024).
• Media-filled bed units like the iAVs are ideal for small-scale farming and research purposes (Wang 2024).

Some notes on those citations:

• The statement that an iAVs can yield more than 50 kg of tilapia per year per cubic meter is supported by the iAVs research if “per cubic meter of water” is interpreted as per cubic meter of the fish culture volume. Yields up to 133 kg/m³/year have been reported for fish culture volume.
• The statement that an iAVs can yield approximately 360 kg of tomatoes or other fruits and vegetables per year per cubic meter of water is supported if “per cubic meter of water” is interpreted as per cubic meter of total annual water input, as sources report yields of up to 400 kg of vegetables per cubic meter of water input.