If you have a planted tank, or any live aquarium plants, you probably also have aquarium snails. A couple are no big deal, but a couple snails will quickly grow to way too many in your fish tank. They always seem to be a pain to get rid of too. There’s chemical treatments that contain copper, but it can harm things like shrimp and I don’t like to add chemicals if I don’t have to.
Another option I tried to get rid of aquarium snails is to get an assassin snail, which hunts and eats other snails. I got one of those and it quickly disappeared into the jungle at the back of my tank. I have no idea what it’s up to.
Finally, I saw this gizmo on Deal Extreme today. A snail trap! It’s a simple design really, the snails are able to creep into the dome shaped container, but then can’t navigate out. Just let it collect your problem mollusks in the dome and then dump it out.