Family Tilapia Farming Unit. Part 1.

What the system includes

• Main tank: 1000 liters (about 264 gallons), circular, resistant to corrosion and UV rays, with a sturdy lid. It holds the water and the fish; the lid prevents evaporation and protects against predators.

• Aeration blower: high efficiency, under 30 W in normal mode, with an air filter; runs on solar power via an adapter. It oxygenates the water, essential for the fish and for the biofloc.

• Submersible pump: 12 V DC, quiet, low consumption, rated capacity of 2000 liters per hour, with a filter to prevent clogging. It circulates the water through the filters and the tank, 24 hours a day.

• Filter 1, settler: standard 55-gallon drum (208 liters), with a removable basket and a bottomless bucket in the center, made of durable impact-resistant plastic. It removes large particles and sediment; solids settle in the center.

• Filter 2, mechanical: standard 55-gallon drum (208 liters), with a replaceable 100-micron mesh, easy to wash and reuse, and a transparent body. It captures the smallest particles; the transparent body lets you see the condition of the filter.

• Filter 3, biofilter: container of approximately 100 liters (about 25 gallons), smaller than the 55-gallon drums, with 15 to 20 liters of K1 bio balls (no less, to have enough surface area). It houses the nitrifying bacteria; it is a moving bed filter.

• Pipes and connections: 3-inch PVC pipe, UV resistant; quick-connect T fittings, with or without glue. They carry the water between the components of the system.

• Reservoir: bucket of approximately 20 liters (about 5 gallons), smaller than the biofilter container, with a lid and a direct connection to the system. It stores additional water; the submersible pump goes inside the reservoir.

• Additional materials: kit of connections and adapters, flow control valves, maintenance tool kit, test strips. Assembly, control and monitoring of the system.

• Measuring kit: pH meter, reagents for ammonia, nitrites and nitrates, submersible thermometer, dissolved oxygen meter. For measuring water quality.

How the water circulates

The full route is shown in the two figures below.

What you need to know about the biofilter

• It is a moving bed filter: the bio balls must be kept moving with the aeration, especially where the slots of the drain pipe are.

• The inlet and outlet should be as far apart as possible, so the water has more processing time.

• The drain pipe has slots in its lower half: they let the water in and keep the bio balls from going down the drain.

• K1 bio balls are zero maintenance and last indefinitely. As a less efficient alternative, soda bottle caps can be used.

• The biofilter drain has a T with an accessible top cap: if it clogs, it can be unclogged from above.

• Cover the biofilter and the other filters with something easy to remove: the sun damages the bacteria and turns the water green.

What you need to know about the pump

• The flow rate must be 100% of the tank volume per hour in real flow, not the nominal figure on the box: for a 1000-liter tank, the pump must move 1000 real liters per hour.

• A second backup pump is recommended: if one fails, the other keeps the system going and gives you time to repair it.

• The circulation cannot stop: it runs 24 hours a day, every day, because it keeps the system's bacteria alive.

What you need to know about aeration

• Place the diffuser as far as possible from the drain: if it is close, the freshly oxygenated water goes straight to the filter and is not used in the tank.

• Generate the bubbles from the middle of the tank downward; better from the bottom. The diffuser hose must be weighted (for example, with a bottle acting as a weight) to stay submerged.

• Do not rely on the falling water to oxygenate: it is only secondary oxygenation.

The location

• You can install the system outdoors under cover, but it performs better indoors: there you produce all year round, even in winter, with the environment under control.

• Choose a place without direct sunlight on the tank, to avoid overheating the water and excessive algae growth.

• Level, solid surface, so the system stays stable.

• Easy access to electricity (for the pump and the blower) and to water nearby (to fill the system).

• Away from sources of contaminants and predators. Install the protective screen when the tank is ready.

• Indoors, install lights that mimic the natural sunlight cycle, keep good ventilation to prevent the accumulation of toxic gases and use heating in winter to keep the water between 24 to 30 °C.

• Indoors you also reduce evaporation and protect the system from dust, leaves and predators.

Assembly, step by step

1. Place the 1000-liter tank higher than the first filter, well seated and stable, with a slight incline toward the drain side, so waste accumulates next to the suction point.

2. Leave an intact rim of 10 to 15 cm around the entire perimeter of the tank, without cutting it down to the edge: this makes it very difficult for the fish to jump out. If it is cut down to the edge, it would have to be covered with a mesh.

3. Place filter 1 at a slightly lower height than the tank; filter 2 a little lower than the first; and filter 3, the smallest, at the end of the system. Each stage sits lower than the previous one: the water flows down by gravity.

4. Connect the tank and the three filters with 3-inch PVC pipe and T fittings. The T is preferred over the 90° elbow: the T does not get blocked by an air bubble because it works as a vent, it lets you see if it is blocked and, if it gets blocked below, the water rises and exits through the other outlet toward the next filter.

5. Overflow drainage: inside the tank, the drain pipe is L-shaped. One section runs along the bottom, with slots, and from there the side section rises to the PVC T at the upper outlet. The fish feces enter through the slots in the bottom section, rise through the side pipe and exit by overflow through the T, toward the first filter. The slots keep fry or small fish from getting out.

6. Connect the outlet pipes of the first and second filters, ensuring adequate flow toward the next components.

7. The water return enters on the farthest possible side from the drain: that way the return zone is the clean zone and it pushes the water toward the dirty zone. Follow the labels indicating the water flow to avoid mistakes during installation.

8. Place the blower in a dry, elevated place. Connect the air pipe to the blower and secure it with clamps.

9. Direct the air to the 1000-liter tank and to the biofilter, with diffusers for even distribution.

10. Place the submersible pump inside the reservoir.

11. Check that all connections are firm and leak-free.

The pipes, at a glance

The other pipes go exactly as in the drawing of the complete system (Figure 1).

Initial tests

1. Before filling the system, visually inspect all connections: no leaks or stress points in the pipes.

2. Fill the tank with 1000 liters of clean water. Check that the water flows by gravity from the tank to the filters.

3. Turn on the water pump and the blower. Watch how the water flows through the three filters and that the air bubbles are continuous in the biofilter.

4. Final check: no leaks and all components working properly, with constant circulation of water and air. Do not add the fish yet.

How to prepare the Seed Ferment (day 1)

Visual summary of the preparation.

Rules during maturation

• There are commercial inoculants in bottles or powder to mature the system faster, but bacteria are free: you only need to colonize them once.

• You can also attract the nitrifying bacteria with food and no fish.

• Measure the parameters daily during maturation. On day 16, all of them must be within the recommended ranges before stocking the fingerlings.

• Urea is handled with gloves and kept out of reach of children.

Species and density

• Recommended species: Nile tilapia (Oreochromis niloticus), especially in California. It is resistant to pH and temperature variations, grows fast, converts feed well and resists common diseases.

• Density: 60 to 80 fingerlings per cubic meter of water (approximately 1000 liters). It is recommended to start with 60; with experience, it can be taken up to 80. More than 80 raises ammonia and nitrites, stresses the fish, increases the risk of disease and reduces growth through competition.

• In California, aquaculture must be registered with the Department of Fish and Wildlife (CDFW) and comply with current regulations: confirm the local requirements before buying fingerlings.

Acclimation

1. When you receive the fingerlings, inspect them visually: no unusual spots, damaged fins or abnormal behavior. During transport, avoid exposing them to direct sunlight or sudden movements.

2. Place the bags or containers with the fingerlings floating in the tank for 15 to 20 minutes, to equalize the temperature and avoid thermal shock.

3. Open the bags and add small amounts (approximately 250 ml) of tank water every 5 minutes.

4. After about 30 minutes of acclimation, gently tilt the bag so the fingerlings swim out slowly and on their own into the tank. Do not pour the water from the bag directly into the tank: it may contain waste or contaminants from transport.

5. Watch their behavior during the first hours: they should swim actively. If they stay at the bottom of the tank or swim erratically, check the water parameters immediately (pH, temperature, oxygen and ammonia) and adjust as needed.

6. During the first 24 hours, do not feed the fingerlings: this way they adapt without generating additional waste.

After acclimation

• Monitor the parameters daily during the first two weeks. When they stabilize, measure every two days and, when the system is completely stable, weekly.

• Keep a stable environment, without sudden changes in the water parameters; constant aeration; and avoid handling the fingerlings unnecessarily during the first days.

• If nitrate levels start to rise over time, you can add aquatic plants to the system and turn it into aquaponics: the plants use nitrates as fertilizer.

• If you notice stress or abnormal behavior, check the problems and solutions section of the second article.

First feeding

• Start after 24 hours in the tank. Use high-quality powdered or granulated feed, with 35 to 40% protein.

• Feed 2 to 3 times a day in small amounts, making sure all the feed is consumed within a few minutes. If they do not consume all the feed, reduce the amount.

Feeding plan by stage

• Fingerlings (0 to 1 month): powder or microparticles, 35 to 40% protein, 3 to 4 times a day, approximately 10 to 15% of their body weight per day.

• Juveniles (1 to 3 months): granules, 30 to 35% protein, 2 to 3 times a day, approximately 5 to 7% of their body weight per day.

• Adults (over 3 months): larger pellets, 25 to 30% protein, 2 times a day, approximately 2 to 3% of their body weight per day.

• Use floating feed: it lets you see how much they consume and avoids waste, which destabilizes the system.

• Feed in the morning and at the end of the afternoon, when the water temperature is most suitable and the fish are most active.

• Give only the amount the fish can consume in about 5 to 10 minutes. If there are leftovers, adjust the amount at the next feeding.

• Do not overfeed: excess feed generates waste that raises ammonia and nitrites.

Maintenance ferments

Ferments provide carbon and microorganisms that keep the biofloc in balance. Prepare them in advance.

Visual summary of the ferments.

Cleaning filters and equipment

Filter 1: settler (every week)

1. Stop the water pump so no water enters the filter during cleaning.

2. Open the drain valve located at the bottom of the filter.

3. Collect the cloudy water in a container: you can use it as fertilizer for trees or shrubs.

4. Add the same amount of clean water to the system to maintain the level.

Filter 2: mechanical (every week)

1. Follow steps 1 and 2 for filter 1.

2. Take the mesh out of the filter and rinse it carefully with clean water (no chlorine or soap) somewhere else.

3. Put the mesh back in the filter.

4. Top up the water level in the system.

Filter 3: biofilter (only after each harvest)

• It does not need deep cleaning: the aeration and the bacteria keep it clean.

• Do a visual inspection to check for any obvious obstruction.

• Do not remove the bio balls from the filter: they house the colony of beneficial bacteria. Excessive rinsing or removing them affects the biological balance of the system.

Equipment: regular check

• Blower: check daily that it works properly and that there is a good distribution of bubbles in the tank.

• Water pump: check weekly that it is in good condition and that there are no obstructions in the pipes.

• Pipes and connections: inspect them for leaks or blockages.

Log

Write down the amount of feed, the measurements of the water parameters, the maintenance tasks performed and observations on the health of the fish. Use a table with date, amounts, parameter levels and observations.

You now have the system built, the water matured and your first fingerlings swimming and eating. The hard work is behind you: now it is time to care for them. In the second article you will see how to monitor the water so nothing slips past you, how to harvest your tilapia when they reach their weight, what to do if something goes off normal and how much the whole system costs.