Aquaponics is a sustainable food production system combining conventional aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks) with hydroponics (cultivating plants in water) in a symbiotic environment. In aquaculture, effluents accumulate in the water, increasing toxicity for the fish. This water is led to a hydroponic system where the by-products from the aquaculture are broken down by nitrogen-fixing bacteria, then filtered out by the plants as nutrients, after which the cleaned water is recirculated back to the animals.
In an aquaponic system, nutrient-rich waste water from fish in rearing tanks is used to provide plant food to vegetables and herbs grown hydroponically in grow-beds. Plants in the grow-beds grow rapidly in response to dissolved nutrients that are excreted by the fish, as well as the micro-climate within the greenhouse. These concentrations of dissolved nutrients approach the quality found in traditional hydroponic systems. Fish excrete nitrogen through their gills in the form of ammonia, and bacteria converts the ammonia into nitrites which in turn are converted to nitrates. Nitrates are the preferred form of nitrogen for the efficient growth of fruiting vegetables. The removal of nutrients (fish waste, algae and fish feed leftovers) from the water by the plants allows the freshly cleaned water to be recirculated back into the fish tank. A series of pipes, irrigation fittings, stands and water pump/s enable this process to be self-contained in a recirculating system.
Long before the term “aquaponics” was coined in the 1970s, the Aztec Indians raised plants on rafts on the surface of a lake. This occurred circa 1 000 A.D. In modern time, aquaponics emerged from the aquaculture industry as fish farmers were exploring methods of raising fish while trying to decrease their dependence on the land, water and other resources. Traditionally fish were raised in large ponds or in netted pens off ocean coastlines, but in the past 35 years much progress has been made in recirculating aquaculture systems (RAS). The advantage of RAS is that fish can be stocked much more densely: 1 fish for every 10l of water, thus using only a fraction of the water and space to grow the same amount of fish as pond- or netting-based systems. The early aquaculture systems battled with the problem of the accumulation of fish waste, but in the 1970s research on using plants as a natural filter began, most notably by Dr. James Rakocy at the University of the Virgin Islands. The first-large scale commercial aquaponics facility, Bioshelters in Amherst, MA, was established in the mid-80s and is still in operation today.