Aquaponics is the combination of two well-known food production methods, aquaculture and hydroponics, functioning together in a semi-symbiotic manner. The word "aquaponics" is a word blend, or better stated, a portmanteau that attempts to more precisely describe the practice of integrated aquaculture (growing aquatic animals like fish, mussels, crayfish and others in combination with plants). The "aqua" portion comes from aquaculture, and the "ponics" portion comes from hydroponics. In other words...
....Aquaponics = Aquaculture + Hydroponics. So, let's take a look at the two growing methods that form the foundation of aquaponics.
Recirculating Aquaculture Systems (RAS)
Recirculating aquaculture systems (RAS) are capable of efficiently producing massive amounts of fish and other aquatic livestock in a very small footprint. However, the organisms (fish, crayfish, mussels, etc.) in these systems produce a copious amount of nitrogenous waste, which becomes increasingly toxic to these inhabitants as it builds up in the system. In order for the fish to survive and continue growing, this waste must be dealt with. A well designed RAS will include mechanical filtration and bio filtration components. The mechanical filtration removes solids (fish excrement, bacterial floc, algae, etc.). Next, bio filtration converts toxic ammonia in the water to nitrite and then to nitrate by utilizing nitrifying bacteria. Nitrate is far less toxic to fish than ammonia and nitrite, but it still must be dealt with, otherwise it will continue to accumulate. In extremely high concentrations, it too can be toxic to fish, and there is a risk that it can "revert" back into toxic forms if left in the system.
Methods to reduce these nitrogenous compounds can include partial water replacement, chemical treatment and fairly elaborate off-gassing systems. As you can imagine, handling, treating and removing these nitrogenous wastes can represent a considerable expense when running a traditional RAS system. Aquaponics seeks to turn this "negative" into a "positive" by utilizing plants to remove the nitrogen, primarily in nitrate form, from the system. Essentially, when you harvest plants from the system, you are removing nitrogen. So what was once an "expense" can potentially be a "profit".
Hydroponics gardening is a method of growing plants using mineral nutrient solutions in water, without soil. Terrestrial plants may be grown with their roots in direct contact with nutrient solution or in an inert medium, such as expanded clay, gravel, mineral wool (rock wool), perlite, vermiculite, coconut husks, etc. Hydroponics systems are capable of producing massive amounts of plant mass in a high density, controlled environment. However, the nutrient inputs tend to be quite expensive, and require fairly routine flushing and replenishment. The flushed chemical solution is still quite high in nutrients, particularly nitrogen and concentrated minerals, leading to concerns of proper and ecologically responsible disposal. Aquaponics seeks to provide the bulk of the nutrients required for hydroponic systems via fish waste.
The Two Become One
There is no doubt that both recirculating aquaculture and hydroponics are extremely efficient methods of producing food in their own right, but by combining the two methods in the form of aquaponics, we seek to more fully utilize the "waste" from both methods, and thereby gain efficiency that neither method would technically achieve on its own. It is important to note that beneficial nitrifying bacteria are what really make an aquaponics system work. Nitrifying bacteria are quite literally the tie that binds the aquaculture and hydroponics components together, allowing them to work together. While it is entirely possible to establish this bacterial population (called cycling) with fish present, we strongly encourage first-time aquaponics growers to establish a strong population of these beneficial bacteria prior to stocking fish (called fishless cycling).
I'll leave you with a quote from Gary Donaldson, author of The Urban Aquaponics Manual: "While fish and plants are the visible biological elements of an aquaponics system, beneficial bacteria are the key to its successful operation."
Edited by kellenw (show revisions)