Aquaponics essentially works to imitate the real biological cycle in maybe an outdoor pond or pool.
First you have your fish and then above the fish is your growbed. Both are connected through a series of pumps and tubes so that the fish have water to survive as well as the plants. The fish waste is used by the plants (not directly, only after beneficial bacteria has transformed the waste into nitrites) and in turn the biofiltered water from the plants is reused by the fish.
The aquaponics revolution is catching on with full steam in Australia, especially parts where they have a severe drought. This is because aquaponics uses about 90% less water than a traditional aquaponics or hydroponics operation uses. Because the water is treated biologically there’s no need to throw out used water. The only water that’s lost when you’re growing fish and crops using an aquaponics system is from evaporation – which is somewhere in the range of 5%.