Backyard Aquaponics

Aquaponics is essentially the combination of Aquaculture and Hydroponics. Both aquaculture and hydroponics have some down sides, hydroponics requires expensive nutrients to feed the plants, and also requires periodic flushing of the systems which can lead to waste disposal issues. Re-circulating aquaculture needs to have excess nutrients removed from the system, normally this means that a percentage of the water is removed, generally on a daily basis.

This nutrient rich water then needs to be disposed of and replaced with clean fresh water. While re-circulating aquaculture and hydroponics are both very efficient methods of producing fish and vegetables, when we look at combining the two, these negative aspects are turned into positives. The positive aspects of both aquaculture and hydroponics are retained and the negative aspects no longer exist. Aquaponics can be as simple or as complex as you’d like to make it, the simple system pictured above is made from one IBC (Intermediate Bulk Container). The top was cut off and turned upside down to become a growbed for the plants. Water is pumped up from the fish tank into the growbed. The water trickles down through the media, past the roots of the plants before draining back into the fish tank.

The plants extract the water and nutrients they need to grow, cleaning the water for the fish. There are bacteria that live on the surface of the growbed media. These bacteria convert ammonia wastes from the fish into nitrates that can be used by the plants. The conversion of ammonia into nitrates is often termed “the nitrogen cycle”. This will be dealt with in more detail elsewhere on this website.

Growbeds filled with a media such as gravel or expanded clay pebbles are a common method of growing plants in an aquaponic system, but there are many different methods that can be used. In fact any method of hydroponic growing can be adapted to aquaponics. Plants can be grown in floating foam rafts that sit on the water surface. Vegetables can also be grown using NFT (Nutrient Film Technique), or through various other methods using a “run to waste” style of growing. This is done by removing a percentage of the fish water each day and watering vegetables planted in different media such as coir peat, vermiculite, perlite etc.

Many different species of fish can be grown in an aquaponic system, and your species selection will depend on a number of factors including your local government regulations. Quite high stocking densities of fish can be grown in an aquaponic system, and because of the recirculating nature of the systems very little water is used. Research has shown that an aquaponic system uses about 1/10th of the water used to grow vegetables in the ground. An aquaponic system can be incredibly productive. I’ve produced 50kg of fish, and hundreds of kilograms of vegetables within 6 months in an area about the size of your average carport, 8m x 4m.

This is a system that requires no bending, no weeding, no fertilizers, and only uses about the same power it takes to run a couple of light globes.

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