Aquaponics is the combination of aquaculture and hydroponics. Aquaculture involves the raising of aquatic animals such as various types of fish. Hydroponics involves the growing of plants with nutrient rich water instead of a soil medium. A video that gives a great description of how aquaponics works can be found here:

Inner cities are known for being classified as food deserts due to the lack of supermarkets available to provide fresh foods. The increasing implementation of aquaponics provides one solution for this problem. An advantage of aquaponics is that it reduces the amount of water inputs necessary to 1/10 that of a conventional farm because it naturally recycles the water already in use. It also reduces the amount of land area needed because such system can be stacked vertically. This allows aquaponic farms to exist in inner cities and provide residents with much needed healthy fresh foods.