Hi,

In the beginning (before there was Aquaponics), there was aquaculture.

These photos illustrate a basic recirculating aquaculture system (RAS).....a tank, a pump and a bio-filter (or two).

The addition of a growing system is what makes this an Aquaponics system.

The bio-filters used in this system are recycled pickle drums filled with oyster shells. The water is pumped from the tank into the top of the bio-filter where it percolates down through the oyster shell media. The Nitrosomonas bacteria that have colonised the bio-filters convert the ammonia that is passed by the fish into nitrites. A second type of bacteria (Nitrobacter) converts the nitrites to nitrates (plant food).

In a straight RAS, the build up of nitrates......which (unlike ammonia and nitrites) are not toxic.......is avoided by regular water replacement.

Where the water is dumped, there is an environmental issue. Where it is used to irrigate crops, it is sustainable.

Gary