Aquaponics is one of the oldest, and most effective self-sustainable human made environments for farming out there. It involves growing crops using nutrients that derive from fish excreta.
Aztecs would use a proto-aquaponics system that involved planting crops on stationary islands in waters. The fish in the waters would provide nutrients to the plants floating, and whenever they were ready to be picked, the ancient farmers would boat around the rivers to gather their harvest. The system can be used in a variety of facets, from large scale farms to small time apartment herb gardens.
Aquaponics: From Small-Time to Big Fish, Friendly Aquaponics, Inc.
sproutabout: Like always, if you have questions, feel free to ask. Not too long ago, I wrote an article on Aquaponics for the website greenanswers.com. Check it out for further information.