How to properly start an aquaponic system ?

Aquaponics refers to an ecosystem where fish and plants grow together in symbiosis. In practice, you raise fish in a pond and grow plants in a substrate or on the water, without soil . The fish waste, rich in ammonia, is broken down by nitrifying bacteria into nitrites and then nitrates, nutrients that can be assimilated by plants. The plants absorb these nitrates for their growth and thus clean the water, which is continuously recycled back to the fish pond.

This closed-loop system is very water-efficient , with up to 95% savings compared to conventional open-ground cultivation, as the water is constantly recycled. Aquaponics thus makes it possible to produce vegetables (and possibly fish) in a sustainable, local and fun way.

Before you begin, determine what type of aquaponics system is right for you. There are three common methods : grow bed (substrate), floating raft (DWC), and nutrient film technique (NFT).

1) The growing bed consists of a tray filled with substrate (gravel, clay balls, etc.) into which water from the basin is pumped and then flows back down, feeding the plants. This system is very versatile and allows a wide variety of plants to be grown, with a stable environment for the roots. This system is very tolerant of unforeseen events : for example, in the event of a pump failure, the moist substrate provides a reserve for the plants, which can survive for a certain time without water circulation.

2) The raft (floating system) uses a tank where foam rafts with holes for plant pots float. The roots are permanently immersed in the water in the tank. This system is ideal for fast-growing leafy vegetables (lettuce, basil, etc.).

3) NFT (Nutrient Film Technique) circulates a thin stream of nutrient-rich water through long pipes or gutters where the plants are placed. It allows vertical cultivation on several levels of pipes and is well suited to small plants (strawberries, herbs).

Which method is best for beginners ? For hobbyists, a grow bed is often recommended because it naturally incorporates biofiltration thanks to the substrate populated with bacteria. In other words, a substrate bed is a simpler and more robust way to start.

A fish tank : This can be an aquarium, a food-grade plastic tub, a barrel, or any other watertight container. It's best to start with a medium-sized tank (200 L or more) to ensure a stable ecosystem.

A plant growing tray : This is where your vegetables will grow. Its size should be proportional to the size of the fish tank. This tray will be filled with substrate (for a grow bed system) or will support the NFT rafts or pipes, depending on the method chosen.

A growing medium (if using a grow bed) : essential for stabilizing plants and harboring bacteria. The most commonly used substrates are expanded clay balls, non-calcareous rolled gravel, or pozzolan.

A water pump : This circulates water from the pond to the growing tank continuously or intermittently. Choose a pump that is suitable for the volume of water to be mixed (it should be able to pump the entire volume of the pond in one hour, typically).

Pipes and fittings : to connect the pump to the growing tank and allow gravity flow of water back to the pond. 13 mm (1/2") PVC pipe is often suitable. Also, plan a drainage system for the growing tank (an overflow or siphon) to prevent overflow and ensure the flood/drain cycle if necessary.

An aeration system (depending on the case),: Often, mixing the water with the pump is enough to properly oxygenate the pond. However, if the fish density is high or the water volume is large, an air pump with a diffuser (bubbler) can be useful to enrich the water with oxygen.

Aquaponics can be installed both indoors and outdoors , provided that a few criteria are met. Light is the first factor to consider. Placing the system in a well-lit, naturally lit area is ideal, as plants need sufficient sunlight on a daily basis. Place your system away from shadows (away from north-facing walls, trees, or hedges that would cast shade).

In an apartment without outdoor space, you can install the system near a sunny window. And if the light is insufficient, it is possible to invest in artificial grow lights (horticultural LEDs) to supplement natural light.

The other important criterion is the ambient temperature. In temperate climates, an outdoor system works well from spring to fall, but winter poses a challenge. If you install your aquaponics system outside, plan to be able to bring the system indoors in winter (garage, veranda) or protect fish and plants from frost.

Ideally, if you have the option, you should build or use a greenhouse. A dedicated aquaponics greenhouse allows you to maintain a favorable microclimate year-round, your fish and plants will be protected from the elements and cold, while still receiving sunlight.

Place the pool in a stable, level location that's easy to access for maintenance. Finally, provide a secure electrical outlet nearby to power the pump (and lighting if needed).

Once the equipment is in place and the location is chosen, you need to start the system's biological cycle before adding all your fish and plants. This is to give the nitrifying bacteria time to colonize the filter and transform the nitrogenous waste. First, fill your pond with water (preferably dechlorinated or left to stand for 24 hours to evaporate the chlorine). Turn on the pump to circulate the water.

At first, introduce very little life: ideally, do a dry cycle (without fish) or with one or two robust feeder fish. Monitor the evolution of the water quality each week using tests : after 1 to 2 weeks, the level of ammonia toxins will rise then fall in favor of nitrites, then nitrates will appear.

This process typically takes 4 to 6 weeks for sufficient bacterial balance to establish. Be patient !

Wait until the tests show 0 mg/L of ammonia and nitrites, a sign that the biological filter is doing its job, and a few dozen mg/L of nitrates (a non-toxic nutrient consumed by plants). You can then gradually add your fish to the pond (preferably during a mild period in spring or autumn, outside of heat waves or frost).

Introduce a few fish at a time, spacing them out over several days, so as not to saturate the system all at once. Similarly, gradually plant your growing tank with easy-to-use young plants (lettuce, basil, mint, etc.) so that they begin to absorb nitrates.

During these first few weeks, monitor your setup daily : check that the pump is running continuously, that the water remains clear, and measure the pH and toxins every 2–3 days. The ideal pH is between ~6.5 and 7.5 to suit both fish and plants. Once the nitrogen cycle is established, your aquaponics system is officially "cycled" !

Clean, well-oxygenated water at the right temperature and balanced in nutrients keeps fish and plants healthy. Test the water regularly (pH, ammonia, nitrites, nitrates) and be ready to intervene if something goes wrong (for example, a nitrite spike that needs to be corrected by a partial water change).

Feed your fish sparingly : Overfeeding is a common mistake. It can be tempting to overindulge, but excess uneaten food decomposes and causes ammonia levels to skyrocket, throwing the fish out of balance and potentially poisoning the entire system. A good rule of thumb is to only feed as much as the fish can eat in 2 to 3 minutes, even if it means splitting up the meals. In aquariums, the recommended basic density is about 1 cm of fish per liter of water.

Common mistakes to avoid : Skipping cycling or adding sensitive fish too quickly is a guarantee of problems (diseases, mortality).

Going too fast or too big : Don't start with a huge, complex system. A small unit of 200–500 L is ideal for beginners: large enough to be stable, but still easy to manage.

Neglecting routine maintenance : Although aquaponics requires little daily maintenance, a quick daily inspection is important. Check that the pump is working, that the water level is correct (regularly compensate for evaporation), that the fish are eating well and showing no signs of stress. Remove dead leaves from the plants, and make sure no pipes are blocked by debris.