Photo courtesy of AIDG
If you hang out with gardening hippies, you may hear the term “aquaponics” thrown around. So, what the heck does it mean?
Aquaponics is a gardening technique designed to maximize water efficiency and minimize the need for fertilizers. The technique involves farming and raising fish in an integrated system, where fish produce natural fertilizer while plants filter and oxygenate the water. A well designed aquaponic system requires minimal supervision and creates two desirable crops – fresh herbs and fish. The components of the system produce synergy: fish and plants grow more efficiently together than they would in separate tanks.
…when the aquaponic system is fully operational after six months, it leaps ahead of inorganic hydroponics. This leads to earlier maturity of greenhouse crops under aquaponics and much heavier cropping.
Aquaponics is a portmanteau of the words Aquaculture and Hydroponics. It gets improved results due to the symbiotic behavior of several living organisms. The plants and fish complement each other, but a lot of the productivity depends on integrating bacteria and microorganisms in the system. Bacteria convert fish waste into useful nutrients for the plants, and phytoplankton produce food for the fish.
Aquaponics is an old concept – the ancient Aztecs and Egyptians used the technique with various plant and fish species. In China and Thailand, it’s traditional to raise fish in flooded rice paddies. Since the 1970’s, several universities have been developing modern techniques and applying scientific method to get the greatest performance.
Compared to conventional agriculture, aquaponics is a huge water saver. On a farm in Oklahoma, it takes 6 gallons of water to grow a head of lettuce. At 24 heads per case, that means raising 1,250 cases of lettuce using conventional methods would require 180,000 gallons of water. A DeepWater aquaponic system uses about 16.1% as much water to create the same results (and it generates more than 3,600 pounds of fish fillets and 7,400 pounds of fish scraps for use as fish feed or fertilizer).
Here’s some more information on aquaponic water efficiency, comparing aquaponics to hydroponics and conventional farming techniques:
Estimated total value of output is then A$405,000 ($305,491 USD) — which represents water use efficiency of around 173 liters/A$100 of production.
This compares very favorably with the Australian commercial hydroponics figure of 600 liters of water used per A$100 of production.
There are many different aquaponic systems, but two major schools have emerged. These two approaches look very different, and each is best for certain crops or locations. These competing systems are Deep Water Aquaponics and Reciprocating Aquaponics. The primary difference is where the plants are positioned. In Deep Water Aquaponics, plants float on top of a pond of water (usually inside styrofoam rafts with holes for their roots). In Reciprocating Aquaponic systems, the plants are outside the pond and water is carried to their roots along irrigation tubes.
Photo courtesy of Aria Fotografia at Flickr.com
Deep Water Aquaponics is also known as Raft Culture Hydroponics or “the UVI system”. One of the main proponents of this type of hydroponics is Dr. James Rakocy of the University of the Virgin Islands. He offers training courses and maintains an aquaponic demonstration facility with 15 full scale systems that have been in continuous operation for several years. The system is very productive and water efficient:
UVI’s aquaponics system, which occupies an eighth of an acre and uses 29,000 gallons of water, can produce annually 11,000 pounds of tilapia and 11,000 pounds of basil or 1,250 cases of lettuce.
Here’s a cool photo-tour of the UVI system. Note – the fish are grown in separate tanks to prevent them from eating the roots of crop plants.
Reciprocating Aquaponics is also known as “Flood and Drain” or “Ebb and Flow”. This system uses gravel or sand beds to filter water from fish tanks, and then irrigates plant beds using irrigation pipes (or positions plant roots inside the irrigation pipes). The result is a system with more control over temperature and humidity. Some plants that don’t do well in hydroponic systems thrive in these conditions, because their roots are protected against rotting. Biofiltration beds also allow more microbial activity in a smaller area, which is important when space is limited. On the flip side, the filtering media will get clogged over time, and cleaning it is hard work.
If you’re looking for a cool way to renovate the pool in your back yard, or if you want to do more with the rain water in your rainbarrels, there’s no time like the present to check out an aquaponic system.
Photo courtesy of ideonexus at Flickr.com