Aquaponics is where fish and plants are grown in a combined system. The system uses nutrient rich water provided by the fish and circulates it through to a grow bed to feed the plants.
Aquaponics works with the aid of the good bacteria in your ponds. Fish produce waste and ammonia in the pond, which is toxic to them. The bacteria converts the ammonia into nitrite and then into nitrate, which plants use as a growing nutrient. This nutrient rich water is pumped to a grow bed for the plants, which then filter and clean the water for the fish. So with aquaponics you can grow fish and plants to eat.