Attach a length of plastic tubing between the aquarium pump and a three-gang valve. Attach three pieces of plastic tubing the other side of the gang valve, making sure they are long enough to reach to the bottom of a 5-gallon bucket. Attach air bubblers to each of the three pieces of tubing.
Fill a piece of cheesecloth with enough compost to fill 4" of the bottom of the bucket. Place the compost in the bucket, making sure the three bubblers are underneath. Fill the bucket with dechlorinated water almost to the top. Add 1/2 cup unsulfured molasses, which will feed the bacteria in the compost.