Get a 2 liter bottle. Drill a hole in the cap. Put airline through the hole and seal it with silicone. Put sugar, yeast, and water in the bottle and shake it up. Put the other end of the airline in the tank and boom, homemade co2.
Also, keep in mind that a reactor and a diffuser are two completely different things. The "reactor" produces the co2, and the diffuser dissolves it into the water. If I have time tomorrow, I'll take some pictures of my DIY setup and post them here.
Last edited by Apocalypse; 01-14-2011 at 12:35 AM.