iAVs in 30 Steps

Introduction

This guide covers the basics of iAVs without going into the complexities of construction or the finer points of plant and fish care. Keep in mind that each location has unique environmental factors that may require tailored approaches. Some sections may require basic building skills not covered here, so consulting with a professional is recommended.

iAVs is designed to be easy to build and run without requiring any technical knowledge. Villagers in remote Africa with no formal education have successfully operated these systems, demonstrating how achievable iAVs can be for people from all walks of life.

Step 1 – Select a Suitable Location

You need at least 12 hours of light every day for your plants. Choose a location that is free from shade or large obstacles that may obstruct sunlight.
iAVs needs to have suitable weather for the plants and fish. It is recommended to protect the system against flooding or extreme weather, such as strong winds or heavy rain, and to also cover the fish tank with shade cloth.

Step 2 – Design the Layout

In its simplest (and ideal) layout, iAVs has its fish tank(s) located in-ground. The pump, which is situated in the fish tank, moves water up to the sand bed. The water then percolates down through the sand and drains back into the fish tank. This design uses gravity to return the water to the fish tank and does not need extra plumbing or parts. In the event a water pump or timer is faulty and stuck in the ‘on’ position, any overflow can flow directly back into the fish tank. There is no stand-pipe, overflow or bell siphon used.

Step 3 – Plan the Area

Ensure the location will not be flooded.

Step 4 – Dig The Hole

The ideal place for a fish tank is to be dug into the ground, this uses minimal parts/materials, is easier to build and costs less money. Dig the hole for the fish tank and use the soil to help support the grow bed and build the perimeter walls (if needed). A 1000L tank is recommended for beginners.

An in-ground fish tank is recommended as the best option for iAVs as it is more stable and benefits from the earth’s natural insulation which helps maintain stable water temperatures.

Tanks with flat bottoms or sharp corners can trap ‘waste’ and debris, resulting in poor water quality and creating dead zones with limited water flow. The recommended tank shape is a catenary, which looks like a ‘U’ or a ‘V’ shape from the side view and eliminates dead zones in corners and ensures all of the fish ‘waste’ is collected and then removed.

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.

If placing the fish tank in the ground is not feasible, the system can be modified to include a sump tank which is a water collection reservoir positioned at the lowest point in the system. A float switch activates the water pump when the water levels rise and the water is returned to the fish tank.

While a sump tank can offer certain advantages, it also introduces an additional potential point of failure to the system, a float switch should be also connected to the water pump in the fish tank as protection from water levels dropping too low if the sump pump fails.

The picture above shows a sump which sends the drainage from the biofilters back to the fish tank, which is on the ground (not pictured).

Step 5 – Insert Liner

The fish tank will need a food safe liner. EPDM is the highest quality but is the most expensive. Insert the liner, fold sections to avoid creases and leave out of direct sunlight.

Step 6 – Setup Water Pump

Choose a pump capable of emptying the tank in an hour at the rated head height. Submersible pond pumps are cheap and easy to use but it is recommended to select a quality pump. A pump with a digital controller or app removes the need for a timer or a valve to adjust the water flow.

Insert the water pump into the lowest section of the fish tank. Connect a flexible hose to the pump and ensure it is long enough to reach the far end of the grow bed.

Step 7 – Setup the Float Switch (Optional)

A float switch is optional but highly recommended as protection to prevent the water in the fish tank from being completely emptied. A ‘cable’ float switch can be installed easily without an electrician.

When using a ‘cable’ float switch, plug it into the timer and then plug the water pump into the cable connected to the float switch. Do not turn the water pump on when it is not in the water. If you are not using a float switch then plug the water pump directly into the timer.

Step 8 – Build or Install the Grow Bed

You can build your own grow bed or purchase a pre-made one. The grow bed is filled with sand, to support the plants, and to also serve as the both biological and mechanical filter for your system. There is no other filtration needed, which saves space, reduces costs and is easier to run.

The depth of the sand should be 30cm minimum. The height of the grow bed should be at least 40cm to allow for freeboard and prevent water overflowing.

The bottom of the biofilter must have a slope to allow for complete drainage of water to prevent anaerobic zones. The recommended slope is a drop of 20 millimeters (0.79 inches) for every meter (3.28 feet) in length.

The standard dimensions are approximately 1.2 meters (about 4 feet) in width and range from 3 to 6 meters (approximately 3 to 10 feet) in length. These sizes are easier to manage and allow an operator to easily reach at least halfway across the bed.

The in-ground option is recommended for iAVs. It’s the easiest and most cost-effective way to build a biofilter.

In-Ground:
The in-ground option is considered the simplest and most economical approach to constructing an iAVs but it may not be suitable for regions with high water tables or a history of flooding.

On-Ground:
The on-ground installation option is more convenient to set up compared to the underground option, as it eliminates the need for excavation. , although it does necessitate the construction of biofilter walls. It is more accessible for maintenance and harvesting purposes.

Above-Ground:
The above-ground option is the most costly and difficult to construct due to the need for a robust supporting structure to support the weight of the sand.

Step 9 – Insert Liner

Minimize folds and creases, and ensure any visible parts of the liner are protected from direct sunlight. A liner is not needed if you purchase a pre-made grow bed.

Step 10 – Setup the Drainage

A slit drain is a narrow horizontal gap on the drainage end of the grow bed.

The photo above shows an example of a slit drain.

A slit drain is cost-effective, it eliminates the need for additional drainage materials and efficiently reduces pressure on the water to prevent sand from exiting the biofilter.

The picture (left) shows a plywood biofilter (without the liner) with a slit drain cut from end to end.

Drainage Fittings
When a slit drain is not appropriate various types of other fittings and methods can be utilized in iAVs although they are not recommended.

Flange Fittings:

These are bolted to the underside of an above-ground biofilter and can be bought from specialist aquaculture suppliers.

Sink Drains:

These are ideal for bottom drains on biofilters.

Ebb & Flow Fittings:

These fittings are obtained from hydroponics suppliers and are suited to small biofilters.

Puddle Drains:

These come in a variety of sizes and are readily available and inexpensive.

Sand Retention

You can prevent sand from escaping by placing a layer of shade cloth over the drainage outlet, covered by a small amount of medium-sized gravel. This will help keep the sand in place. Do not use weed mat or cloth such as geo fabric as it could cause issues with clogging.

Step 11 – Setup Plumbing

Connect the flexible hose to the far end of the grow bed and secure it. Add in a convenient valve if the water pump does not have a controller.

Note: A valve is not needed if the water pump has a controller.

Step 12 – Test & Purchase Sand

The sand should meet the specifications required for making concrete and is often referred to as washed builders sand, sharp sand, or horticultural sand. It needs to have no fine sand, no silt, and no clay. Suitable sand can be found at landscape yards, quarries and big hardware retailers.

Beach sand is not recommended because it can raise the pH levels. The ideal sand for use in iAVs looks and feels like common table salt or raw sugar. If faced with a choice between sand that is too fine or too coarse, it is generally better to choose the coarse option.

Select some samples of sand to test and purchase the best type. The sand must be inert and can be tested with some vinegar. A basic jar test can be used to test the amounts of sand, silt and clay.

Testing

Confirming the suitability of a sand sample for use in an iAVs is a simple process that involves a series of straightforward field tests:

Vinegar Test

Inert sand does not react with water, meaning that the pH of the water should remain unchanged when it comes into contact with the sand.

To test the sand’s inertness, follow these steps:

Place a small amount of sand (about 1 cup) in a glass or ceramic bowl.
Pour white vinegar over the sand until it is fully submerged.
Observe the reaction for 1-2 minutes.

If the sand is inert, there should be no visible reaction, such as bubbling or fizzing. If you notice any reaction, the sand is not suitable for use in an iAVs .

Turbidity

Turbidity is the cloudiness of water caused by the presence of silt or clay particles.

To perform the turbidity test, fill a glass jar or drink bottle halfway with sand, add water until it reaches the top, then shake vigorously for 5 to 10 seconds. Place the jar on a bench and allow the contents to settle.

This sample suggests the presence of clay. This would be confirmed if the water remained cloudy for longer than a few minutes.

Differential Settling

Next, leave the jar and its contents undisturbed for several hours. Once the sand has settled, any silt will appear as a dark line on top of the sand, as shown in the photo below. The smallest particles, clay, will settle last, forming a pale layer above the silt.

The black line on the surface of the sand is silt. The floating black layer is organic matter.

This sample is free of silt and clay. Note the small amount of powdered sand on the surface. The black lines in this photo are refracted light – not silt.

Step 13 – Fill the Grow Bed

Fill the grow bed with sand, the depth on the shallow end should be 30cm. Using a 3 meter grow bed with a slope (on the bottom) of 2 cm per meter, the depth of sand at the deep end will be 35cm.

Step 14 – Check pH of Source Water

Use potable water. Adjust the pH of the water to 6.4 (plus or minus 0.4) before adding it into the fish tank.

You will need a pH testing kit or pH meter. The optimal pH for iAVs is 6.4 (slightly acidic). If your source water is not the correct pH you will need to lower it using phosphoric acid, or raise it by using potassium hydroxide or calcium hydroxide.

Note: In a well-established iAVs, minor pH fluctuations are typically self-corrected by natural processes within the system, however, it is still recommended to check and record the pH at least once a week.

Step 15 – Prepare the Power Outlet & Program the Timer

Plug the multi-board connector into the ground fault circuit interrupter (GFI) and plug the GFI into the power outlet. Use an extension lead if needed so the power board can reach the water and air pump. Ensure the power is turned off and leave it off until later.

Note: Seek professional advice to ensure your electrical connections are in a safe position protected from the weather.

A timer automatically controls when the water pump is turned on and off. Follow the instructions in the manufacturers manual and program the ‘on’ periods so the timer turns on for 15 minutes at 6am, 8am, 10am, 12pm, 2pm, 4pm, 6pm and 8pm. Plug it into the power board.

Note: If using a smart plug or a water pump with a digital controller you can use that instead of a timer.

Irrigation Schedule

The beds are irrigated for 10-20m every 2 hours, during the day only, 15 minutes is usually adequate to ensure the sand is fully saturated . There is no irrigation at night, this saves electricity and allows adequate oxygen for microbes to proliferate.

At 6:00 am, the timer triggers the pump, and the nutrient-rich water enters the sand bed and immediately begins to run along the furrows and percolate down through the sand.

Within 2 to 10 minutes, water will begin to flow out of the sand bed to drain back into the water tank.
After +/-15 minutes, the water will be at the top of the sand (but below the top of the ridges) and the pump is shut off.

Note: The flow rate and delivered volume need to be adjusted so that the water does not reach the base of the plants.

For the next 1 hour and 45 minutes, the bed is allowed to fully drain and remain drained.
At 8:00 am, the pump starts again, and it runs for +/- 15 minutes and then stops.

This process is repeated every two hours during the hours of daylight. The number of events per day will depend on your latitude and the season.

In the tropics, the first cycle can begin somewhat before dawn and the last cycle can start at dusk (finishing just after total darkness).

Step 16 – Connect Air Tubing and Air Stones

An air pump with built-in battery backup is recommended in case of a power failure (when connected to the grid). An air pump is also recommended for protection in case the water pump fails and extra aeration during the night when there is no water being pumped into the grow bed. Ceramic stones are the best choice for air stones.

Air Stones are positioned along the longer sides of a fish tank about half way down.

Step 17 – Add Water into the Fish Tank

Add the water into the fish tank. When the tank is filled half way you can check that the water pump and air pump are working by turning them on briefly.

Clean drinking water.
Rainwater is usually the best choice.
Top up the tank once a week if required, or when the water level is reduced to 75%.

Potable water from the municipal supply is a suitable option however, it may contain chemicals such as chlorine or chloramine, both of which are not ideal for plant health and should be treated before use.

Chlorine is easy to remove by allowing the water to stand in an open container in sunlight, where it will gas off. Chloramine is the more persistent disinfectant, but it can be removed with the use of vitamin C tablets.

Step 18 – Build & Install Manifold (Optional)

A manifold reduces the velocity of the water and is recommended. Build a manifold and drill a hole in one of the caps for the water hose.

Install the manifold and insert the hose connected to the water pump. Insert a valve into the water hose at a convenient location. Check that the manifold is level and secured in place and then test it by turning the water pump on.

Note: If the water pump has a controller you will not need a valve.

Step 19 – Flood the Grow Bed & Level Sand

Fill the grow bed with water and use the water to level the sand and then turn the water pump off when the grow bed is flooded and the sand is level.

Step 20 – Build the Furrows & Ridges

Ridges are raised areas that plants are grown in and keep the base of the plants dry which reduce the risks of root rot or other diseases. Ridges also act as ‘ventilation stacks’ during the irrigation cycle when the furrows are flooded and air is forced to escape upwards out through the ridges. Ridges are easily shaped by hand, or using basic materials like wood or PVC pipe.

Furrows are grooves in the surface of the sand where the water from the fish tank is irrigated and the fish ‘waste’ is deposited where it is exposed to oxygen to hasten decomposition. Furrow irrigation ensures each plant gets equal access to moisture and nutrients.

Creating Furrows

To create the first furrow, you can 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. It is important that the furrows are level so the water (and nutrients) is distributed evenly to each plant which removes competition amongst plants.

Step 21 – Inoculate the Grow Beds (Optional)

Tiny organisms, or microbes, in the sand break down the fish waste and turn it into a form that plants love can use. Modern aquaponic systems rely on nitrifying bacteria but iAVs relies on the complex diversity of soil microbes to make the nutrients available to the plants. Soil microbes do not lead to as much acidification of the water, helping to reduce or remove the need to adjust the pH. iAVs utilizes 100% of the fish ‘waste’ and reduces or removes the need to supplement with extra fertilizers compared to other system types that do not utilize all of the fish waste, which leads to deficiencies.

When setting up a new system, sprinkle a small handful of mature compost or humus-rich soil, into the furrows nearest the water inlet end.

You don’t need much—just a couple of tablespoons per furrow should be enough to get things started.

Step 22 – Irrigation Test

Test the amount of water/ irrigation cycle and adjust if needed using the valve ensuring the furrows are flooded, the sand is saturated and the ridges are not flooded and there is no water overflowing.

Step 23 – Check pH, Check Timer & Activate Air Pump

Do a final check of the pH. Ensure the timer is set at the correct time and the water pump is plugged into it. You can now turn the air pump on and leave it to stay on.

Step 24 – Select & Purchase Fish Food

A commercial fish feed is recommended. Feed twice per day, with the last feed not later than 2:00pm. (earlier in the tropics or hemispheric winter). Use floating pellets so you can monitor the amounts and remove any uneaten food.

Use a high quality fish food preferably without additives.
Feed the fish twice a day as much as they will eat in 10 minutes.
Do not overfeed the fish.

Step 25 – Purchase & Add Fish

Start with 80 to 100 x 15g fish per 1000 liters. The iAVs research used Tilapia but other types of fish can be used as long as they eat a lot and are suitable for your local climate conditions.

Purchase fish and gradually introduce the fingerlings to their new environment to minimize stress and increase their chance of adapting successfully to their new home.

Step 26 – Add Plants

Plants absorb the nutrients and clean the water for the fish. Grow a mixture of leafy greens, and legumes, but have at least 50% of the growing area in fruit-bearing crops. Avoid growing mostly lettuce and other leaf crops. Transplant plants into the grow beds.

A diverse range of plant species can thrive in iAVs, including vegetables, fruits, herbs, and root crops.
Plants should be at different stages of growth, not all very young or very mature.
Growing only one type of plant may lead to an imbalance in nutrients.

Detritus & Algae

Detritus is a layer of organic matter and algae that forms in the furrows where it is exposed to oxygen which accelerates the decomposition of the fish ‘waste’.

Step 27 – Fish Feeding Times

6:30 am: Feed the fish the amount they will consume within 10 minutes. Remove any unwanted food. Keep a note of how much they eat so you know how much to feed them next time. Adjust the levels as needed.
1:45 pm: Feed the fish again as per the previous instructions.

Do not feed the fish after 2:00pm.
Do not overfeed the fish.
Floating pellets make it easier to observe feeding behavior and to remove any uneaten food.

Step 28 – Fish Feeder (Optional):

If needed, an automatic fish feeder takes care of feeding the fish. However feeding should be done manually as much as possible to observe fish behavior and the amount they eat.

Note: Be sure to check it regularly and beware of cheap brands that may be unreliable.

Step 29 – Fish: Harvesting

As fish get bigger, they need more room to swim around. So, it’s important to remove some fish to either eat them, move them to a different tank. If you don’t do this, the tank can get too crowded, which can stress out the fish, make them sick, and slow down their growth.
When they get to 250 – 300 grams (in about 3-4 months), you can start harvesting the largest ones incrementally (perhaps weekly) and at some point harvest the remainder and start over. This cycle could take 9-12 months. The fish can be eaten, or relocated to another tank.

Step 30 – Monitor

Test the pH and water quality. A mature system buffers the pH and changes are not needed but it is recommended to check the pH regularly. A test kit can be used to periodically check the ammonia levels.

Check the irrigation cycles and ensure the timer is working. Reshape the furrows and ridges if needed.

Monitor fish feeding amounts and adjust if needed.

Like any farming method, iAVs is not immune to pests and diseases. Refer to the guide on Integrated Pest Management. Only use aquaculture-safe remedies. Regardless, avoid letting the spray enter the water.

Notes:

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. It has been easily implemented by villagers in Africa that could not speak English.

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.

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.