I've been drinking a lot of plain seltzer water lately (unflavored), see. And here at my desk I have a small 2 gal aquarium with 5 Tetra fish. The water has evaporated about 2", and I just keep wondering what would happen if I poured some of the seltzer in. Bottled seltzer may actually be more pure than tap water. I think about this a lot. (Roughly 30 minutes total, broken up throughout the day). I don't want to harm the fish. Their names are "1", "2", "3", "4" and "5" - easy to remember, but that's not important right now.