actually snails are quite good in an aquarium, if you know how to control them. First, DO NOT OVERFEED your fish. The left over food will be a feast that the snails are shure to enjoy! Second, remove any dead leaves that might have began to rot, as this is a food source as well. If their population ever goes out of control, try to put slices of lettuce in your aquarium, weighted down to the bottom. The snails will soon cover it, and you can remove it, together with the snails. Some german made traps are also available, so try Google. Generally, if you keep your aquarium clean and well maintained, you wont have much of a problem. The snails that I have and really recommend are Malaysian Trumpet Snails; they do not eat plants, and live of algea and some residue that might be found. They bury themselves into the ground during the day (they may only be visible sometimes during daylight) and come out in their full power during the night. Sand is recommended, if not obligatory, for these species. They even indicate oxygen levels- if you suddenly see a great migration of snails to the top of the tank, that means that oxygen is missing in the water! (Fish will also do this; if little O2 is present, they will "gasp" at the top of the tank) Overall, snails are pretty good janitors, if you keep them under control.
