Tilapia are typically the fish of choice for these types of systems only because they can reach a marketable size in as few as five months and are reproductive as early as 12 weeks under optimal conditions. Tilapia are a warm water fish in that they prefer temperatures between 82-90 degrees for optimal growth, this is their primary disadvantage in many areas due to extreme weather conditions during the winter months. But tanks may be insulated and covered as long as there is sufficient oxygenation of the water to keep them healthy and active.
Tilapia will often eat practically anything! If housed outdoors in the warmer months they will eat algae which may rapidly form in their tanks if exposed to sunlight. They will also eat vegetable scraps, dog food kibble but it must be fed in moderation or it will quickly foul the water, trout and catfish chow, duckweed, earthworms, phoenix worms and a variety of other foodstuffs.
With sufficient oxygenation of the water Styrofoam sheets may be used as rafts to grow lettuce and other greens in. The seeds are placed in a hydroponic media such as rockwool cubes that are then placed into holes cut into the Styrofoam. As the plants grow they are thinned out on these sheets and again set to float in the fish tubs. This provides some extra insulation to keep the tanks warm as well as providing a stable platform to grow more food! The Tilapia will eat some of the growing roots but as long as you are feeding them it should not become a problem.
These systems can also be done "off grid" by using solar or wind energy to run the aerators, water pumps and heating systems for the fish. Newer more energy efficient equipment is being designed every day and this years pumps and equipment are more energy efficient than last years. I see this improving year after year as we strive for more energy efficiency in our day to day lives.
Indoors you do not need expensive high power grow lights to keep your plants healthy. Today's low wattage fluorescent lighting is a safe and effective alternative for most plants over high wattage high pressure sodium bulbs. For every 2 bulb fluorescent lighting fixture you will use one cool white bulb and one warm white bulb, these lighting fixtures can be hung within inches of the tops of growing produce for a safe and low cost method of providing sufficient light for optimal plant growth.
What is the bridge I talked about earlier?
The bridge is a U shaped pipe that is inverted placed between the fish tank and the sump. It acts as a siphon that draws the solid waste from the bottom of the fish tank and deposits it into the sump.
How does this work?
For the top portion of the inverted U somewhere in the center of it you drill a small hole and place an airway check valve into this hole (and glue it into place using aquarium sealant), then attach a piece of air line tubing to the end of that. This check valve when used on an aquarium air pump stops water from flowing back into the pump during a power failure. We are using it in a slightly different way, when placed into the pvc pipe we want this check valve set so that you can suck air through the tubing but air can't flow back into the pvc pipe. Next you will make sure that the down pipe on the fish tank side reaches almost to the bottom, to this you will attach a T connector, to this T connector. See fig. 2 Once this bridge is placed into the tank (and the ends of the pvc pipe under water) you will need to suck on the air line tubing till you see a water flow in your clear tubing, then tie off the end with a twist tie. This will need to be repeated from time to time, in order to maintain suction between the two tanks.