How to Build & Operate an iAVs

One of the most remarkable aspects of iAVs is its simplicity and accessibility. Villagers with no formal education have successfully operated these systems, demonstrating how achievable iAVs can be for people from all walks of life.

This guide aims to show that anyone can set up and maintain an iAVs, regardless of background or resources. With a little guidance, this sustainable technology can be implemented in diverse settings, from small backyard gardens to community and commercial farms.

Building and operating an Integrated AquaVegeculture System (iAVs) involves several key steps and components. Here’s a simplified guide based on the information from our iAVs EBook:

  1. Fish Tank: The system starts with a fish tank. The fish are fed, and they produce ‘waste’. This ‘waste’ is a rich source of nutrients that plants can use to grow. One of the simplest fish tanks is a hole dug in the ground, with the upper/above ground-level perimeter lined with bricks or cinder blocks, and then lined with a waterproof liner such as polyethylene plastic, EPDM or any other food-safe impermeable liner. Concrete and cinder block need to be coated to prevent leaching.
  2. Fish Tank Design: Fish tanks should be designed with simplicity, efficiency, and gravity flow in mind. This also minimizes the need for extra equipment and energy. Having a fish tank in the ground is recommended as the best option for an iAVdue to several reasons: simplicity and cost-effectiveness, structural integrity, thermal stability, and efficient waste removal. The most effective designs include a parabolic cross-section with an ovoid or rounded rectangle in plan, or intermediate designs with sloped (45-degree pitch) or “V” (or “U”) bottom cross-sections and rounded-rectilinear plans.
  3. Air pump and Air Stones: Ceramic stones are the best choice for this purpose.
  4. Water: Use potable water. Adjust water pH to 6.4 (plus or minus 0.4). 
  5. Fish: Start with 80 to 100 x 15g fish per 1000 liters. Grow them to 250 to 300 g, then start to harvest larger fish.
  6. Fish Selection: The iAVs research primarily focuses on Tilapia, but various fish species can be used depending on local conditions, such as temperature. It is essential to choose a suitable fish species for your specific environment to ensure the success of your iAVs. If your goal is to sell fish into the local market, then select species that the locals prefer/purchase (at the size and form they expect).
  7. Feed: A commercial feed is recommended. Feed twice per day, with the last feed not later than 2:00pm. (earlier in the tropics or hemispheric winter).
  8. Water Pump: Choose a pump capable of emptying the tank in an hour at the rated head height. Pump 25 to 30% of tank volume (15-20 min ON) once every 2 hours starting at dawn, with no pumping at night.
  9. Timer: A timer will help you maintain the correct watering schedule.
  10. Intermittent Irrigation: The beds are irrigated for 15-20m every 2 hours, during the day only. The filtration/irrigation event should be repeated at regular intervals during daylight hours for as many as eight times per day. This provides abundant oxygen for the plants and microbes.
  11. Sand: The sand should meet the specifications required for iAVs, washed builders sand.
  12. Biofilter: These biofilter is filled with sand and will house your plants and serve as the both biological and mechanical filter for your system. The nutrient-rich water is then pumped into a sand bed (biofilter) where the plants are growing. The sand acts like a sponge, holding onto the water and nutrients long enough for the plants to absorb them. 
  13. Furrows: The fish ‘waste’ is deposited in the top layer of the furrows where it is exposed to oxygen to hasten decomposition.
  14. Microbes: The fish ‘waste’ is then broken down by tiny organisms called microbes. These microbes take the fish ‘waste’ and convert it into a form that plants can use as food. 
  15. Ridges: Act as ventilation stacks and keep the crown of the plants dry.
  16. Plants: The plants, in turn, absorb these nutrients, which helps them grow. As they absorb the nutrients, they also clean the water, removing the ‘waste’ products and making the water safe for the fish again. Grow a mixture of leafy greens, and legumes, but have at least 50% of the growing area in fruit-bearing crops. Grow plant species with high nutrient demand requirements in proportion to feed input composition. Avoid growing mostly lettuce and other leaf crops.
  17. Light: Provide at least 12 hours of light per day. More light is better, but this is plant species-dependent.
  18. Clean Water: The water, now clean, is returned to the fish tank, and the cycle begins again.  Water is ‘reused’ from at least 100 to over 300 times before being ‘lost’ to transpiration or incorporated into food.
  19. Water Quality Management: It’s important to monitor key water quality parameters such as ammonia, nitrite, pH, dissolved oxygen, and temperature regularly to ensure that they remain within acceptable ranges for the species of fish being raised. Testing kits are available to measure these parameters and should be used frequently. A mature system buffers the pH and changes should not be needed.
  20. Pests & Diseases: Integrated Pest Management is crucial for maintaining the health and productivity of an iAVs.

It’s important to note that successfully operating an iAVs requires some managerial skill, which can come with experience. The system is relatively “user-friendly” and well buffered against rapid changes in water chemistry.

Some previous gardening/husbandry experience on the part of the prospective operator is considered highly desirable. Minimal training in general aquaculture management, pest prevention and mitigation techniques, and simple water quality monitoring techniques is recommended for first-time operators.

The longer an iAVs (actually a miniature, managed, and complete ecosystem) is allowed to mature (continuously operated without interruption in, or an excess, in feed input rate), the more stable it will tend to become (biologically and chemically). Also over time, operator(s) gain experience in balancing inputs with outputs and refine (develop) management skills which further increase productivity.

Typically, iAVs facilities develop into functionally mature ecosystems within three months from initialization and are considered to be fully mature following one-year of continuous management/operation.

Remember, every location poses unique climatic, soil, and water conditions that require adaptive solutions. Therefore, it’s crucial to understand the local conditions and adapt the system accordingly.

Please note that this is a general guide and the specifics may vary depending on your local conditions and the specific species of fish and plants you choose to use. 

If you strictly follow the prescribed method, you can expect outcomes akin to those showcased by Mark McMurtry in his research trials, and later by Boone Mora in his successful commercial trial sponsored by the USDA.

Furrows & Ridges

Furrows and ridges are integral components of iAVs. They are designed to facilitate the efficient distribution of water and nutrients to the plants, and to support the formation of a beneficial microbial ecosystem. Here’s what you need to know and do about furrows and ridges:

Creating Furrows and Ridges:

  1. Fill the beds with the correct type and particle size range of sand. Level off the sand relative to the top of the sand bed sides. You can use a simple screed made from plywood for easy leveling, or flood the bed and use the surface of the water to level the sand.
  2. The furrows must be perfectly level to ensure an even distribution of water and nutrients throughout the biofilter. To create the first furrow, use your hands or a hoe to drag the sand up onto the ridge that separates the furrows. Repeat this process for the second furrow, ensuring appropriate spacing. This process should be repeated on the other side of the sand bed.
  3. An alternative way to create furrows is to use a former – effectively a mirror image of the furrow, shaped from plywood or rigid plastic. Dragging the former through the sand will produce evenly spaced furrows very quickly. By the time you’re finished, you should have all the furrows connected at both ends for even water distribution.

Furrows: Detritus Formation:
When initially introduced, sand is inert and devoid of life, which allows water to flow through it without hindrance. However, as the sand comes into contact with fish ‘waste’, a layer of detritus begins to form. This detritus layer alters the direction of water movement from vertical to more lateral. Beneath this layer, a complex network of soil microbes starts to colonize the sand.

These microbes are shielded and nourished by the accumulating detritus. As mycorrhizae, a type of beneficial fungi, develop, they cause the loose sand grains to bond together. This process results in the formation of a firm matrix just below the surface of the sand. This transformation is a crucial part of iAVs.

Furrows: Size and Spacing:
The size and spacing of furrows are largely determined by the crops being grown. For example, single-stem indeterminate tomatoes might require a spacing of 4 plants per square meter, while leaf or herb crops might need a denser planting of 12 or 16 plants (or more) per square meter.

Furrows should be spaced 30-60 cm (12-24 inches) apart and be created between all rows of plants and around the entire perimeter of the system. This provides for the even distribution of water and nutrients over the entire biofilter surface, and similar access for each individual plant.

Furrows: Water Distribution:
The purpose of the furrows is to ensure that during each intermittent irrigation event, the water is channeled rapidly and efficiently across the entire bed. As the water flows through the furrows, it guarantees that every plant has equal access to the essential nutrients and moisture needed for optimal growth. This helps to maintain a balanced ecosystem and also helps to conserve water by allowing it to soak into the sand (through the sloped sides of the furrow/ridges) rather quickly rather than evaporating.

Furrows: Plant Growth:
Furrows benefit the plants by providing a way for water and nutrients to be delivered directly to the roots. This helps promote healthy root growth, which in turn supports strong and healthy plant growth overall. Additionally, furrows can help reduce competition between plants by creating distinct areas where each plant has access to its own resources.

Ridges: Biofilter Gaseous Exchange:
The ridges formed between furrows function as ‘chimneys’ which facilitates gaseous exchange (oxygenation) of the soil atmosphere.  This dramatically benefits the entire soil microbiology and rhizosphere (plant nutrient assimilation) by providing for a complete soil atmosphere exchange (oxygen recharge) following each irrigation interval (drainage).  The ridges also function to keep the crowns (base) of the plants dry to eliminate crown rot and mitigate against potential bacterial, fungal and mold contamination of the plant crops. Providing for a complete soil atmosphere recharge following each irrigation cycle eliminates potential development of anaerobic conditions and accelerates microbial metabolic activity and plant nutrient assimilation (growth and yield). 

Irrigation is only during the day.

Irrigation is only conducted during the day when there is enough light for photosynthesis to occur. There are no irrigation schedules at night. This is due to several reasons:

  1. Plant Metabolism: Plants have different metabolic processes occurring in the dark. They do not transpire at night, which means that they are not “taking up” water at night.
  2. Energy Efficiency: Pumping water at night requires more energy than necessary.
  3. Microbial Activity: The roots and rhizosphere processes benefit from abundant oxygen, and all the aerobic soil organisms do also. The “idea” around not flooding at night is to allow time for microbes to proliferate (multiply) and actively metabolize substrate without interruption.
  4. Plant Health: Pumping water at night can potentially harm plant rhizosphere and metabolism.

This also means iAVs  uses only a small amount of electricity and is very suitable for solar applications.

Understanding Potential Yields

It’s important to note that the information provided on yields is based on optimal conditions and specific crop choices. The actual yield can vary significantly based on factors such as the type of crops grown, the local climate, and the skill of the farmer. An optimized system is capable of even higher yields.

 


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How to Build & Operate an iAVs