The Nitrogen Cycle in Aquaponics

Nitrogen is super important for plant growth and therefore the health of your system depends strongly on the efficiency of the bacteria in your system. These bacteria help carry out the nitrogen cycle in aquaponics. Let’s walk through the steps of the cycle to give you a better understanding of how Nitrogen moves through your aquaponic system.

Nitrogen plays a critical role in the survival of living organisms. Nitrogen forms part of amino acids. Amino acids are used to make important proteins. However, nitrogen is often the least available in certain ecosystems. Therefore, we need to ensure that our aquaponics system is supported by a strong bacterial colony. This colony is the trick to assist in making nitrogen available to the plants in the form of nitrate.

Ammonification is the process where nitrogen leaves animals in the form of ammonium. This can happen when the animal excretes, dies or begins the decaying process. Therefore, the ammonification step in aquaponics happens when ammonium (NH₄) is produced. The fish produce ammonium through their fish waste. This can become toxic to the fish in high concentrations. But in a low pH environment like in an aquaponics system, the toxicity is relatively minimal as ammonia is in it’s acidic for NH₃. Now we move on to nitrification. The nitrification step of the nitrogen cycle is broken into two parts.

Part 1: At this step in the cycle the Nitrosomonas bacteria will convert the ammonium into nitrite (NO₂^–). All Nitrification steps take place in your media bed and biofilter. As this is where your bacteria are located.

Part 2: These nitrites are converted into nitrate (NO₃^–) by the bacteria from the Nitrobacter family. When nitrogen is in the form of nitrates, the plants can utilize nitrates for the nitrogen assimilation step in the nitrogen cycle.

Nitrogen Assimilation takes place when living organisms take up nitrogen. Therefore, the nitrogen assimilation step in aquaponics is when the plants take up nitrogen in the form of nitrates. Plants require nitrates for optimal health and would suffer without adequate amounts of nitrogen. Nitrogen is utilized in many important biological processes.

This step of the nitrogen cycle is as simple as our food chain. When we eat plants we gain a certain amount of vitamins, minerals and yes you guessed it nitrogen. When we eat other living organisms like plants and animals, we absorb the nitrogen and it climbs up the food chain. This step completes the nitrogen cycle as the fish will consume their nitrogen through their feed only to excrete it in the form of ammonium.

There are other steps in the nitrogen cycle but these are the ones that apply to the nitrogen cycle in aquaponics. As long as you continue to feed your fish, replenish the water, take care of your biofilter and harvest your produce, then you will enable your aquaponics system to continue carrying out the nitrogen cycle.

We just want to give you a friendly reminder, farmer to farmer: Ammonia and Nitrite levels should be less than 0.75ppm and don’t forget to test weekly.

If you found this article interesting and you wish to learn more about the chemistry behind aquaponics then make sure to check out our blog post.