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Aquaponics Nitrogen Cycle

A quaponics nitrogen cycle is the process whereby the fish waste is consumed by the plants to maintain proper water pH and healthy living conditions for the fish and plants. Without this process the fish would suffer and the plants would also suffer since there would be no nutrients to feed them. This process maybe slightly difficult to grasp for some but if you are familiar with raising fish in a fish bowl or aquarium it is easy to grasp as it is a fairly simple process. Since we all need nitrogen to survive, the whole world acts as a cycle and there is nitrogen in the air, in plants and in animals. Like animals, plants also need nitrogen to survive. In the aquaponics system, the plants receive their nitrates from the fish. The plants in an aquaponics system need a type of nitrate called ammonia. They need this form of nitrate because it can be absorbed by the roots and help the plant grow healthily.

The process is so ingenious that even mother nature herself uses it all the time, in fact it is based on a natural ecosystem that would be found within a pond or aquatic environment. The process is so named because it combines aquaculture – the growing of fish, with the Greek word ponus which means growing without a medium. It is similar to the method of hydroponics many commercial growers use but unlike hydroponics no chemical nutrients or fertilizers have to be used. Instead of using these the nutrients needed are provided by the inhabitants in the tank making this a very environmentally friendly and healthy way of growing food.

To remove the nitrates the waste material is broken down by bacteria and worms that live in the lower levels of the plant grow beds as well as in the fish tank itself. The process is called ammonification. The bacteria use enzymes to break down the harmful waste material into ammonia then into nitrites and ultimately nitrates. Nitrites are still harmful to fish so these bacteria are essential in not only this conversion but also the final step into nitrates. Nitrates are usually chemically engineered or made from bio material as well and added as fertilizer in traditional or hydroponic farming. The bacteria, in their natural life cycle, feed off of the waste ammonia and oxygenate the nitrogen compound, so it is essential that they thrive to make the system work.

The fish in an aquaponics system consume their food and their nutrients and in turn they will excrete ammonia. Because ammonia can be extremely toxic to fish, the ammonia will need to be converted into Nitrites. The good bacteria in the water complete this process before converting the Nitrites to Nitrates. The Nitrates are then absorbed by the plants’ roots. The water in the tank will eventually evaporate but will be replaced by more water using the aquaponics system. This is a useful cycle which benefits both the plants and the fish. There is very little need to maintain an aquaponics system as it is all done automatically through this cycle.

The plants take in the nitrates through their roots in the grow medium as they would if they were in soil in the natural soil environment. As long as the plant roots have sufficient access to the nutrient rich water the plant will thrive. Within the root nodules of the plant the nitrogen is taken up into the plant leaving the water free of nitrogen compounds. The solid waste is also trapped in the grow bed by the grow medium where it can be broken down by worms into the same nitrates and nitrites for plant use.  As the plants have removed the nitrogen compounds from the water it once again becomes safe for fish to breathe and the cycle continues.

The Aquaponic system cycle is based around the earths own nitrogen cycle whereby plants remove nitrogen compounds and fish excrete nitrogen rich ammonia waste. The process is mutually beneficial allowing both to grow successfully in a polyculture environment. Enzymatic bacteria are essential in the process as they provide the necessary link between the ammonia and the nitrates that plants can absorb through their root system. Each aquaponic system may be set up differently but the process remains the same and with any part of the delicate balance missing it will not function.

Frequent water changes should not be required if the proper pH  level is maintained. If you are familiar with having a fish aquarium this is the same process albeit though the majority of the waste is picked up from the fish by the plants eliminating the need to do water changes. It is recommended that the water pH for an aquaponics system should be between 6.8 and 7.2. This pH range will ensure that the water in the system stays clean, crystal clear and fish tolerant.

It may take a couple of tries to get it right and it is recommended that you start small and gradually increase the fish population as you learn how to maintain the proper pH range and master the aquaponics nitrogen cycle. The ratio of plants and fish in an aquaponics system should be kept at one fish for every four vegetables grown. It is suggested that the fish to plant ratio be 1:4 to maintain proper pH. In the end it all comes down to maintaining the proper balance of fish, plants and water to achieve the desired results.


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