The Role of Bacteria in Aquaponics Explained

Growing up in Suburbia, I never had a reason to pay attention to the required biology and chemistry classes. Lo and behold, I really should have listened in those classes so long ago! After doing some catching up I have been able to put a few things together that all of us can understand when it comes to setting up, cycling, and maintaining a system.

An aquaponics setup requires beneficial bacteria in order for fish and plants to flourish. Plants feed off nutrients supplied by fish refuse and decomposed fish food. Before a plant can absorb these nutrients, they must be converted into nitrates. Two types of bacteria work hand-in-hand to achieve this process. They are Nitrosomonas and Nitrobacter.

Bacteria Growth

Bacteria thrive in the substrate, or rocks, that are usually on the bottom of fish tanks. Rocks are also used as a medium in which to grow aquatic plants. Fish refuse and excess food settles at the bottom of the tank, and the bacteria work on this waste. In an aquaponic system, those “rocks” are not in the fish tank but in the grow bed and it is there that this transformation happens

Ammonia and Nitrosomonas

Excess ammonia is produced in the water when there is an overload of fish and food waste. Ammonia must be removed to keep fish at optimum health. Nitrosomonas bacteria require ammonia to survive. Their role is to convert ammonia to Nitrites. Excessive nitrites can be fatal to fish. To safeguard fish, and to aid in aquatic or aquaponic plant growth, nitrites must be then be converted to nitrates.

Nitrates and Nitrobacter

Nitrobacter bacteria feed off nitrites. Once nitrites are consumed by Nitrobacter, the nitrites are converted to nitrates. Plants rapidly grow when they are absorbing nitrates. The process of converting fish waste to ammonia, then nitrites, and finally nitrates; is called the nitrogen cycle.

It is this balance… the pH factor in the water that you need to continually check and monitor. One way over and you can kill the fish, one way over the other, and the plants will die. The Aquaponics Ecosystem is all about keeping the balance between alkaline and acidity.