Jan 13

Intro to Aquaponics

Aquaponics is the combination of Aquaculture and Hydroponics.  Combining these two systems creates a closed loop system.   Eliminating the environmental impacts caused by disposing of the water solutions in each systems.  In combination these systems work in harmony and create a more sustainable system.

In aquaculture fish are raised in enclosed tanks relying heavily on filtration and chemicals to keep the water viable for the fish.  The water has to be changed out often to alleviate the ammonia and nitrites in the water.  This nutrient water has to be disposed of, often dumped into rivers or streams.  Cleaning this water is expensive and difficult.  This is the main downside to aquaculture, when utilizing monoculture the environmental impacts are huge.

In Hydroponics, plants are grown in nutrient rich water.  This method is reliant on chemicals being added to the water to supply the proper food for the plants.  This method is effective and results in high yields.  Growing plants in this way allows the grower to provide the exact amount of nutrients evenly across a whole system.  The downside to hydroponics is that the water becomes to salinized due to the chemicals added, after a while the water and nutrient mix has to be completely removed.  This has to be disposed of as well.  Then all the tanks and growing medium have to be sterilized.  This process is wasteful and time consuming and the water mixture has negative impacts on the environment where it is dumped.

In an aquaponics system the benefits of aquaculture and hydroponics are utilized; both the high yield in fish production as well as the high yields of produce in hydroponics.  Combining the two systems creates a closed loop.  The waste products from the fish are turned into food for the plants and the plants help purify the water, making it viable for the fish again.

In an aquaponics system the fish effluent builds up in the tank, along with uneaten food then it is converted into ammonia by heterotrophic bacteria.  Too much buildup of ammonia will kill the fish, which is why in a typical aquaculture system the water has to be flushed out and replaced frequently.  The ammonia is converted to nitrites and then the nitrites are converted to nitrates via nitrifying bacteria.  Now as nitrates the plants can use what was originally fish waste as food. After the plants absorb the nitrates the water is again suitable for aquaculture.

There are three main types of Aquaponics systems; Media filled, Nutrient Film Technique and the Raft method.

The media filled method is the most common, especially for the hobby or backyard type system.  In this method plants are grown in gravel, peat, coir, or other medium.  The nutrient rich water flows through these tanks either constantly or on an ebb and flow system.  The media filled method is less complicated than the other two because there is no need for a separate tank for the bacteria to colonize.  In this system the bacteria live in the growing medium.

In the Nutrient Film Technique plants are grown in long channels with a small amount of water flowing over the roots.  In the Raft Method, plants float in rafts over deep channels.  In both of these systems a separate bio filter is required to encourage the nitrifying bacteria to live.  There is a higher volume of water required than in the Raft system vs. the NFT systems.  This extra water helps maintain water quality and enables a slower shift in PH which reduces stress on the fish.  This higher water load however requires more infrastructure to support the weight of the extra water in the grow beds.  A lot of research has been done on the raft method and once up and running can produce very high yields per sq. ft.

By combining the beneficial properties of both aquaponics and hydroponics the negative and costly impacts can be alleviated while maintaining the high yields of both systems. Aquaponics also uses one tenth of the water used in typical farming, which would be a huge benefit anywhere fresh water is a limited resource.   Aquaponics is beneficial in many ways and promises to be part of the solution to our food production needs.