Aquaponics & Aquaculture
Aquaculture is the farming of freshwater and saltwater organisms including molluscs, crustaceans and aquatic plants. Unlike fishing, aquaculture, also known as aquafarming, implies the cultivation of aquatic populations under controlled conditions. Mariculture refers to aquaculture practiced in marine environments. Particular kinds of aquaculture include algaculture (the production of kelp, seaweed and other algae) fish farming, shrimp farming, shellfish farming, and the growing of cultured pearls.
Aquaculture has been used in China since circa 2500 BC. When the waters lowered after river floods, some fishes, mainly carp, were held in artificial lakes. Their brood were later fed using nymphs and silkworm feces, while the fish themselves were eaten as a source of protein. By a fortunate genetic mutation, this early domestication of carp led to the development of goldfish in the Tang Dynasty.
The Hawaiian people practiced aquaculture by constructing fish ponds. A remarkable example from ancient Hawaii is the construction of a fish pond, dating from at least 1,000 years ago, at Alekoko. According to legend, it was constructed by the mythical Menehune. The Japanese practiced cultivation of seaweed by providing bamboo poles and, later, nets and oyster shells to serve as anchoring surfaces for spores. The Romans often bred fish in ponds.
In 2004, the total world production of fisheries was 140.5 million tonnes of which aquaculture contributed 45.5 million tonnes or about 32% of the total world production. The growth rate of worldwide aquaculture has been sustained and rapid, averaging about 8 percent per annum for over thirty years, while the take from wild fisheries has been essentially flat for the last decade.
Aquaponics is based on productive systems as they are found in nature. It can be loosely described as the combination of aquaculture and hydroponics and this is where the name aqua-ponics originates. Backyard Aquaponics Garden gurus 1
|Hydroponic systems rely heavily on the careful application of man-made nutrients for the optimum growth of plants. The nutrients are made from mixing together a concoction of chemicals, salts and trace elements to form the ‘perfect’ balance. Water in hydroponic systems needs to be discharged on periodically, as the salts and chemicals build up in the water which becomes toxic to the plants. Aquaculture systems focus on maximising growth of fish in tank or pond culture.|
The fish are usually heavily stocked in the tanks often, 10kg in 100L of water. The high stocking rates often mean that the tank water becomes polluted with fish effluent which gives off high concentrations of Ammonia. Water has to be discharged at a rate of 10-20% of the total volume in the tank once a day, everyday. This water is often pumped into open streams where it pollutes and destroys waterways.
Aquaponics combines both systems, and in doing so cancels out the negative aspects of each. Instead of adding toxic chemical solutions to grow plants, aquaponics uses highly nutritious fish effluent that contains almost all the required nutrients for optimum growth. Instead of discharging water, aquaponics uses the plants and the media in which they grow to clean and purify the water, after which it is returned to the fish tank. This water can be reused indefinitely and will only need to be replaced when it is lost through transpiration and evaporation.