One drum will be on the floor and on its side between the supports of the stand (this is the fish tank). Cut open the top to allow for oxidization of the tank. A simple wooden stand and legs can be built for this barrel to keep it from rolling over. The other barrel is cut in half to make two smaller ponds on top of the stand. This creates more surface area for growing duckweed and other plants that will feed the fish and clean the water. Cut a hole in the higher staggered barrel (about 3/4 of the way up) for a 1'' PVC to allow the water to flow into the second fish-food barrel. These barrels are staggered to allow for gravity flow. Put about 6'' of gravel in the lower barrel. Cut a hole about 3/4 of the way up in the lower barrel for a PVC pipe to let water flow into the top bed. On the end of this pipe attach the 'T' fitting and another pipe across. Drill some holes in this cross pipe and block the ends so the water can sprinkle down through the holes.
We made the stand from 3'' heavy duty steel pipe because we had it laying around, but something a little less heavy could be used. Bear in mind it has to support 55 gallons of water.