Urban Farming Oz

by Shannida and Matt Herbert

Aquaponics

Aquaponics is a combination of Aquaculture & Hydroponics. Aquaponics uses the water from a fish tank to circulate through a grow bed where the plants are grown. Nitrifying bacteria convert fish wastes into plant-available nutrients. The plants use these nutrients as their main nutrient supply. The fish benefit from this process also, as the water is filtered by the plants, giving the fish clean water to live in. With Aquaponics, both the fish and the plants not only grow well, they flourish.

The process of Aquaponics is a natural interaction between fish and the plants that produces no toxic waste, and does not use any chemical fertilisers or nutrients. Both the plants and the fish contribute to the cycling process of Aquaponics, with the grower using this interaction to their benefit – the fish provide the nutrients for the plants and the plants filter the water so that the fish are able to live. Natural chemicals and the fish food are the only additives to the Aquaponics system.

Benefits of using Aquaponics include:

• Reduced water use
• Reduced chemical use
• Can produce fish and plants for the family / grower all year round, using a greenhouse.
• Compared to conventional Hydroponic growers, Aquaponics does not need to use chemical nutrients for the plants, as the fish waste provides these nutrients to the plants. This eliminates the pollution of waterways, which is usually used to dispose of the eliminated chemical water.
• Compared to conventional Aquaculture growers, an Aquaponics system does not have a build-up of wastes in the system that causes the water to become toxic due to the nitrites. Aquaponics utilises this waste, with the bacteria in the grow beds converting the nitrites into nitrates, which the plants then consume as their main nutrient source.

There have been many studies into the types of plants that can be grown in an Aquaponics system, including leafy green vegetables, vine plants, fruit and fruit trees, flowers and fodder. The cost and turnover time of each crop varies dramatically with leafy greens being able to be produced in a few months, with root based plants and fruit trees taking considerably longer.

Tilapia is the most common fish to be used in Aquaponics systems overseas, although the use of Tilapia in Australia is prohibited due to their ability to overtake and dominate local waterways. Barramundi, Silver Perch, Trout, Golden Perch, Catfish, Murray Cod, Jade Perch, Australian Bass, Black Bream, Eels and Yabbies are suited to the climate in Australia. For more information on the types of fish allowed to be used in Australia in Aquaponics systems, contact the Department of Agriculture, Fisheries and Forestry.

There are 3 main styles of designs in Aquaponics systems including:
Media Based
Deep Flow / Rft
NFT (Nutrient Film Technique)

Media Based is the most common style of Aquaponic design used in backyard systems, Deep Flow / Raft design is used mainly in commercial situations, and NFT is the least used design in both backyards and commercial systems.

Media Based systems use gravel or expanded clay medium located in grow beds where plants are grown direct where they are sown. The grow beds are usually flooded and drained periodically, allowing water to circulate through the system on a regular basis.

Deep Flow / Raft systems are constructed with long channels which hold water at a depth of around 30-40cm depth, with boards that float on top of the water. Boards can be made from styrofoam, plastics, or anything else that you can get to float. Holes are made into the boards, and net pots are fitted. Plants are either sown directly into the net pots, or transplanted from other growing area. The plants grow with their roots always immersed in the long channel of water below the boards.

NFT systems are the least used in Aquaponics, due to its high maintenance needs, including very good mechanical filtration systems needed. Plants hang in net pots much like Deep Flow systems, but instead of a body of water always to hang into, a small amount of water is run along the base of the channel where the plants roots can access it.

There is currently a great deal of interest in Australia about sustainable farming practices including water use, and the degradation of our soils and waterways. Aquaponics uses less water to produce the same amount of food as conventional agriculture, organic agriculture and hydroponics.

As access to water is a critical factor for farming in any country, the use of Aquaponic systems with its low water requirement means that food can be produced in places that it would not normally be grown. Fish from the Aquaculture component of the Aquaponic system can be also harvested, providing fish in areas that do not have natural access to fish in their waterways.

Aquaponics combined with a climate-controlled environment such as a greenhouse, can produce food year round. Another limiting factor for farmers worldwide is access to fertile soils capable of producing quality food. Aquaponics does not need any soils, therefore being able to be utilised almost anywhere in the world.

http://aquaponics.com.au