In a message dated 98-01-31 15:00:47 EST, you write: << ust speculation and curiosity--What if someone were to get a two liter > bottle of diet coke and poke a pin-hole, or a nail-hole in the bottle > and allowed it to slowly mix with the water in the aquarium. Diet Coke > is available at my Lucky's supermarket for as little as 69 cents for a > two-liter bottle when using a Lucky Rewards card. Will this slowly add > carbon dioxide? Will it harm the fish? How about club soda? >> >> Yeah, Ed, go for it. Let me know how fast the fish keel over. But, on the other hand, if you had a crisis-level drop in CO2 (though I can't imagine what that would be) Calistoga or other sparkling water might be added to the tank to "spurt" the level of CO2 short-term. It would probably add some other dissolved solids as well, though, but not sugar, aspertame, or artificial black-water Bob