DIY Diffusion Bell @ petfish.net

Here is a step by step pictorial guide on how to make your own CO2 Diffusion Bell

Getting your materials together. You'll need a small bottle, air hose, suction cup and a check valve.

Cut a piece of the bottom of the bottle off. This will be your "bell."

Next, cut an X in the side towards the top of the bell. Make sure to keep the cuts small enough so that the hose will fit snug. Fold back the cut areas and slide in your hose.

Do the same for your suction cup but in a lower area of the bell and in whichever side is most convenient to hang in your tank.

FYI (for your information) most fish/pet retailers sell bags of suction cups that you can buy. If you can't find them there try a craft store like Michaels or A.C. Moore.

Finally, add your check valve (but not a broken one like mine lol) and connect to your CO2. You now have yourself a diffuser!

I should also add that you're going to want to position this towards the bottom of the tank. You're goal here is to keep the CO2 in the water for as long as posible.