Aquaponics, is a food production system that combines conventional aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks) with hydroponics (cultivating plants in water) in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity.
In an aquaponic system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrification bacteria into nitrates and nitrites, which are utilized by the plants as nutrients. The water is then recirculated back to the aquaculture system. (excerpt from Wikipedia)
I belive that aquaponics gardening is the future of a more self sustainable homestead. The fish provide the plants food and in return the plants feed the fish which then feed you. The great thing about this project is it is easy to build and very scalable. Go as big or as small as you want.
This type of gardening could provide you with a lot of food in the fraction of the space of a regular garden. Great for space challenged people like my self.
Read more here.. Build a Gravity-Based PVC Aquaponic Garden