you could try using a bell. that would be more effiecient with a power head, but even with no power head it would probably be better than just releasing it into the air. just cut the top off a 20oz. (0.5L) soda bottle and let the CO2 bubble up into that. some will still bubble off into the air, possibly, but some will make it to the water, i would think. Cameron ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!