Aquaponics refers to a combination of raising fish or aquatic animals with the growing of plants in water in the same area. The plants benefit from the broken down waste products of the fish (which become plant nutrients) and the aquatic animals get back purified water that is oxygenated and free of toxins. It has been possible to get 4,000lbs/month of food from 1 acre using this system due to production levels increasing up to 10x or more due to its efficiency. Below are a collection of PDFs for those interested in finding out more. There are people charging over $39 for just the bare minimum of info. The first document covers more than what is in the $39 info.