What is Nitrogen Cycle and How its works in Aquaponics

Before building an Aquaponics unit we need to understand a few very important basics. Aquaponics is a system of different species living together in an ecosystem. This habitat has fish, plants and some micro-organisms like bacteria in it. Only someone who understands this one life cycle can take good care of Aquaponics fish farming. We can call this the “Nitrogen cycle”. This video will give you a brief overview of nitrogen cycle in Aquaponics Fish farming  and how it affects the growth of fish.

Let us see what the nitrogen cycle is. An Aquaponics unit consists of three main species.

• Fish growing in water
• Plants growing in the grow beds
• Various bacteria

Feeding the Fishes

When we feed our fishes with pellet feed and other feeds, the fish use a portion of it for their energy and growth. The remaining large part is thrown away as waste. It gets accumulated at the bottom of the pond and dissolves in water. It transforms into ammonia. In addition, the leaves and other wastes that accumulate in the fish pond also rots and turn into ammonia.

Transforming ammonia to Nitrite

Fish waste contains high levels of nitrogen in the form of ammonia. This high level of ammonia is toxic to fish. Similarly, nitrosomonas bacteria decompose this ammonia into nitrite or NO 2-. This nitrite is even more harmful to fish than ammonia. Nitrite in the water can cause fish to die.

Transforming nitrite to nitrate

But this is where we need to understand the importance of a bio filter in an Aquaponics unit. The nitrite formed is used by the nitrobacter bacteria contained in the Aquaponics filter media. Then nitrate or NO3- is released. In order for such a nitrification process to take place, nitrobacter bacteria must be present largely. Biofilters use media such as bio balls and MBBR which provide the surface for the bacteria to grow. At the same time, bacteria need good level of oxygen to grow. Therefore it is necessary to give aeration to the bio filter unit. Initially aeration was not given to this particular filter unit. The nitrification process was very slow at that time. However, the amount of nitrite in this unit reached zero after supplying aeration. The same thing is happening with grow bed media. Bacteria in the water decompose nitrite and convert it to nitrate. A nitrite level in a well-functioning Aquaponics unit is less than 0.5 ppm.

Plants Consuming nitrate

Nitrate is the last molecule in the Nitrogen cycle. Although most fish species do not like to live in high nitrate concentrations, it is less toxic to fish. Fishes are more tolerant to nitrate than ammonia and nitrite to some extent. Nitrate is an important nutrient required for plant growth. So in the Aquaponics unit the nitrate is absorbed by the plants and they grow well and the pure water without nitrate returns to the fish pond. Nitrate levels in a well-functioning Aquaponics unit are between 10 – 100 mg / liter. If the amount of nitrate in the pond is higher, it can be maintained by changing the water a little. Similarly, there is a situation where there are not enough plants in the grow bed which results in high nitrate level. Then planting more plants in the grow bed can solve this problem.

This is the nitrogen cycle in Aquaponics Fish farming unit. With this one activity, fish pond wastes can be removed and fish and vegetables can be grown organically. The pH, ammonia, nitrite and nitrate parameters should be tested regularly to ensure that the water quality in an Aquaponics unit is always maintained at an optimum level. Test kits from various companies are available today. The brands APK and Nice are the main ones. We are using a test kit from a company called Universal Nice. The next video will show you how to test water parameters using this. You can leave your comments and doubts about fish farming below. If you like the video, don’t forget to share it with others and subscribe to the channel. See you again with another video. Thanks