Aquaponics is a blend of aquaculture and hydroponics.
It works because of a bacteria that lives on the gravel that the plants grow in, converting the fish waste (ammonia) into nitrite and nitrate, fertilizing the plants.It is an extremely efficient system using as little as 10% of the water that would normally be required to grow a plant in the soil. The only input is fish food, and of course the dual output is fish and vegetables.
The system that we have built here is large enough to handle up to 700 plate size fish, at present we have 250 Silver Perch, 200 baby Murray Cod, and a variety of herbs and vegetables.