One of the most exciting developments in school-based sustainability technology is creating an aquaponics system.
Aquaponics combines aquaculture and hydroponics to create a food system. In it, plants extract nutrients from the water that they need to grow. In the process, the plants clean water to the benefit of the fish. Fish waste would normally create toxicity in the water, but in an aquaponics system, that waste is fed into a hydroponi system that converts the bacteria into nitrates that the plants use as nutrients. Presto! A full cycle system that actually creates food to eat!
Some definitions to absorb, so to speak:
Aquaculture: raising aquatic animals in tanks
Hydroponics: cultivating plants in water
Aquaponics: A system in which the waste produced by aquatic animals supplies nutrients for plants grown hydroponically (without soil), which in turn purify the water. Can be a closed-loop.