Aquaponic system are recirculating aquaculture systems (RAS) that incorporate the production of plants without soil. Recirculating system are designed to raise large quantities of fish in relatively small volume of water by treating the water to remove toxic waste products and reusing the water many times. The accumulated metabolic by products, like non toxic nutrients and organic matter, need not be wasted if they are channeled into use as secondary crops, terrestrial plants grown in conjunction with fish. This integrated system is referred to as an aquaponic system. The goal is to culture as vegetable that will generate the highest level of income per unit area per unit time. Culinary herbs are the best choice.
In aquaponic systems plants grow rapidly with dissolved nutrients that are excreted directly by fish or generated from the microbial breakdown of fish wastes. In closed recirculating systems with very little daily water exchange, dissolved nutrients accumulate in concentrations similar to those in hydroponic nutrient solutions.
Dissolved nitrogen, in particular, can occur at very high levels in recirculating systems.
- Fish excrete waste nitrogen, in the form of ammonia, directly into the water through their gills.
- Bacteria convert ammonia to nitrite and then to nitrate.
Ammonia and nitrite are toxic to fish, but nitrate relatively harmless and is the preffered form of nitrogen for growing higher plants such as fruiting vegetables.
Aquaponic systems offer several benefits:
- Dissolved waste nutrients are recovered by the plants, reducing discharge to the environtment and extending water use (by removing dissolved nutrients through plant uptake, the water exchange rate can be reduced)
- Minimizing water exchange reduces the costs of operating aquaponic systems in arid climates and heated greenhouses where water or heated water is a significant expense.
- Having a secondary plant crop that receives most of its required nutrients at no cost improves a system’s profit potential. The daily application of fish feed provides a steady supply of nutrients to plants and thereby elimates the need to discharge and replace depleted nutrient solution or adjust nutrient solutions as in hydrophonics.
- The plants remove nutrients from the culture water and eliminate the need for separate and expensive biofilters.
- Aquaphonic systems require substantially less water quality monitoring than separate hydrophonic or RAS.
- Savings are also realized by sharing operational and infrastructural cost such as pumps, reservoirs, heaters and alarm system.
- In addition, the intensive, integrated production of fish and plants require less land than ponds and gardens. Aquaponic system do require a large capital investment, moderate energy inputs and skilled management.
- Niche markets may be required for profitability