Food/Aquaponics
The New Alchemy Institute did a lot of research into aquaculture - small scale production of fish for eating. They found that a fish tank five feet in diameter and five feet tall can produce forty pounds of fish a year. (Meaning that you could have fish for dinner twice a week.) They perfected the method for growing tilapia, catfish or shrimp and even developed computer algorithms which could accurately predict the yield of fish based on variables [1].
Ron Zweig developed a method in which the fish tank doubles as a source of hydroponic vegetables. Vegetables are grown on the surface of the pond so that their roots dangle into the water; the fish fertilize the plants, the plants clean the water, and both can be eaten by humans. This symbiotic growth of aquatic animals and hydroponic plants became known as aquaponics . Aquaponics is a sustainable and extremely resource-efficient method of food production, requiring no input but sunlight.
Algae could also be grown on the surface of the water, providing a source of food for the fish so that they would not require feeding. Many species of algae are also edible by humans.