Food for the fish is the only external input to an AquaPonics system.
Fish transform most of this food into muscle tissue.
But like all animals, fish also produce waste.
Just like in a Recirculated Aquaculture System (RAS), in AquaPonics the waste produced by the fish consisting of settled and dissolved solids is pumped to a bio-filter system.
In this bio-filter, high surface, often porous media through which the water is pumped are colonised by beneficial bacteria.
These natural bacteria convert the waste from the fish tanks, largely ammonia (toxic to fish), first to nitrite (higly toxic to fish) and then to nitrate (not toxic to fish) with the help of oxygen.
It is essential to evacuate these solids from the fish tank as fast as possible to remove ammonia and nitrite (toxic to fish).
If not, they will be colonised by these bacteria, who will also compete with the fish for the oxygen.
Once the full biofiltring cycle is finished, toxicity is reduced to acceptable quantities for the fish.
While not toxic, the accumulation of nitrates causes stress with the fish. For this reason, RAS systems daily renew part of the water, about 10%.
In aquaculture, this highly charged water goes down the drain.
Not so in AquaPonics: here the "charged" water is considered a resource and the connotation turns from negative to positive: the water is no more considered as "charged", but as "rich in nutrients".
These nutrients are then pumped to the hydroponic part where they are absorbed by the plants for their growth.
Both the aquaculture and the hydroponic component complement each other as a single unit.
Most AquaPonics systems use the media in the grow beds as biofilter. The clean water is then recycled to the fish tank.
Some, however, incorporate a separate biofilter.
Other systems allow the nutrients to accumulate in the aquaculture component and only feed the plants the nutrient rich water necessary for their growth.
Here no water is returned to te fish.
This allows to add micronutrients and other products beneficial to plants growth that might endanger the fish. Or to influence the pH so that it is more to the liking of the plants.
It also allows for the addition of chemicals.
Personally I believe these systems to be incompatible with the spirit of AquaPonics which aims to be ecologic, organic and sustainable.
To the best of my knowledge the information I present is accurate. All pages on this website © Hygicell 2009