The Nitrogen Cycle And Aquaponics

Aquaponics is the process of cultivating fish and plants in a closed system to form a sustainable food supply that takes advantage of the synergistic relationship that exists between these two species. The key to a good aquaponics system is to utilize a natural process called the Nitrogen Cycle to create an environment that maintains the quality and fertility of the water so that both fish and plants flourish.

This means creating a system that efficiently processes the waste products given off by fish with very little dependence on outside factors such chemicals, water changes and supplemental filters. To do this, the volume of water, rate of circulation, density of bacteria, fish load and number of plants in the system must be balanced. Out of whack systems could result in excess algae, stunted plant growth, fish deaths and create further work and cost.

In natural habitats, fish populations aren’t extremely dense, while in aquaponics, practitioners regularly attempt to establish much larger concentrations of fish per gallon of water. This is often accomplished through the use of supplemental mechanical and/or chemical purification, but it is desirable from a cost, workload and safety standpoint to balance the system and just enable the natural Nitrogen Cycle to do its work.

When an aquaponics system is at first established, the water is very clear and normally free of harmful substances and bacteria. Once fish are added and begin feeding, the makeup of the water will begin to modify. As with all living creatures, fish use what nutrient elements they require from the food and emit the rest as waste. This waste decomposes in the water and develops into ammonia which is toxic to fish. This is when the Nitrogen Cycle kicks in and begins the biological processes that will in the end take out the ammonia and maintain the quality of the water.

Ammonia is food for certain types of beneficial bacteria. As the ammonia concentration rises in the aquaponics system, these bacteria form, multiply and consume the ammonia. The fish population, depending on numbers and size, produce ammonia at different rates and the bacteria population must be acceptable to consume it at the same rate. As the bacteria consume the ammonia, they give off a waste product of their own called nitrites which are also deadly to fish. At that point a second strain of bacteria consumes the nitrites and changes them to nitrates which at moderate levels are not damaging.

As the system ages, the nitrates accumulate and will eventually reach a difficult concentration. To maintain, sufficient water quality the nitrates have to be removed from the system and maintained at a concentration below 50 PPM. This can be accomplished through frequent water changes which is significant work, but in aquaponics, here’s where the plants come into play. Thru the powers of Mother Nature, plants require nitrogen to grow and they can obtain this necessary mineral chemical by consuming the nitrates. By removing the nitrates the water is made safe for the fish who will continue to feed and emit waste restarting the cycle.

By establishing a suitable equilibrium between the fish and plant populations, water quality can be maintained in an aquaponics system and an abundant harvest of fish and plants can be achieved with the minimal of upkeep effort and cost.

Bob Long is a system engineer who enjoys fishing, professional sports and gardening. He maintains websites on a spread of subjects. If you would like to find out more about aquaponics visit his sites Aquaponics Fish and Tilapia Farming