Before building anything in aquaponics, we must understand the basics. Aquaponics relies on living creatures evolving together in an ecosystem. All animals of this ecosystem play a specific role in a cycle called the “Cycle of Life” or the “Nitrogen Cycle”. The aim of this article is to explain you the nitrogen cycle applied to aquaponics.

1. The food chain

In an ecosystem, all living creatures are evolving together. Every day, some individuals give birth while others die. The living creatures are consume the dead ones. Nothing is lost, nothing is created, everything is transformed. This is the beauty of nature.

2. The Cycle of life

When an animal consumes food, he uses part of it for energy and body growth. He then releases the rest of it into the environment. Those waste are generally composed of nitrogen easily available under the form of ammonia. Then, specific bacteria transform the ammonia in different molecules. In productive ecosystems, the end product is nitrate which is a plant nutrient. Plants consume this nitrate and grow more mass available for the whole ecosystem.

3. Nitrogen cycle applied to aquaponics

In aquaponics, we have 3 key living creatures (and many others slightly less important). They are: The fish, the bacteria and the plants.

3.1. Feeding the fish

nitrogen cycle applied to aquaponics

Fish eating and rejecting fish waste (Nitrogen cycle)

When we feed our fish with pellet food, the fish partially use the food for their metabolism and growth. Another part is released into the water, this is the fish waste.

3.2. Transforming ammonia

Ammonia transformed by nitrosomonas bacteria into nitrite (nitrogen cycle)

Ammonia transformed by nitrosomonas bacteria into nitrite (nitrogen cycle)

Fish waste contains a high concentration of nitrogen under the form of ammonia. Unfortunately, at high concentration, ammonia is toxic for the fish. However, some bacteria (Nitrosomonas sp) present in the aquaponics grow-bed media consume this ammonia. They then release nitrite into the water.

3.3. Transforming nitrite

Nitrite transformed by nitrobacter bacteria into nitrate (nitrogen cycle)

Nitrite transformed by nitrobacter bacteria into nitrate (nitrogen cycle)

Nitrite molecules are also a hazard in the fish tank. Fish can only tolerate them at low concentration. Fortunately, some other bacteria (Nitrobacter sp) living on the aquaponics grow-bed media can eat the nitrite molecules. Finally, those bacteria are releasing nitrate into the water.

3.4. Consuming nitrate

plant consuming nitrate in aquaponics (nitrogen cycle)

plant consuming nitrate in aquaponics (nitrogen cycle)

Nitrate is a very interesting molecule. Even if most fish species don’t like living in high nitrate concentration, it is less toxic for the fish. They indeed tolerate it much better than ammonia or nitrite. Also, nitrate is the main nutrient necessary to plant growth. Therefore, in a well balanced aquaponics system, nitrate are constantly consumed by the plants. Consequently, the concentration in the water remains far below the fish limit.

This is how we apply the nitrogen cycle to aquaponics. It is a simple but efficient cycle allowing to avoid waste and maximize production.

If you want to start aquaponics you must understand this cycle. It is the base of all aquaponics systems. Understanding this cycle will allow you to interpret your water test results and react appropriately.

you will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂