What is aquaponics?

Well rather than reinventing the wheel, here is what the pros have to say:

Aquaponics is based on productive systems as they are found in nature. Aquaponics can be loosely described as the combination of aquaculture and hydroponics and this is where the name aqua-ponics originates.

Hydroponic systems rely on the careful application of man-made nutrients for the optimum growth of plants. The nutrients are made from mixing together a concoction of chemicals, salts and trace elements to form the ‘perfect’ balance. Water in hydroponic systems needs to be discharged on occasion as the salts and chemicals build up in the water which becomes toxic to the plants. Aquaculture systems focus on maximizing growth of fish in tank or pond culture.

The fish are usually heavily stocked in the tanks often, 10kg in 100L of water. The high stocking rates often mean that the tank water becomes polluted with fish effluent which gives off high concentrations of ammonia. Water has to be discharged at a rate of 10-20% of the total volume in the tank once a day, every day. This water is often pumped into open streams where it pollutes and destroys waterways.

Aquaponics combines both systems and in doing so cancels out the negative aspects of each. Instead of adding harmful chemical solutions to grow plants, aquaponics uses highly nutritious fish effluent that contains an almost all the required nutrients for optimum growth. Instead of discharging water, aquaponics uses the plants and the media in which they grow to clean and purify the water, after which it is returned to the fish tank. This water can be reused indefinitely and only has to be replaced when it is lost through transpiration and evaporation.

http://www.backyardaquaponics.com/information.html