Join Date: Aug 2012
Location: Ann Arbor, MI USA
I'm about 75% sure they are pond snails. They truly are harmless. They could actually be viewed as helpful as they eat some algae, detritus and uneaten food. YET, most people treat them like they are about as desirable as a combination of syphyllis and herpes.
If you don't over feed there numbers will decrease after the initial explosion. You can further control it by using the veggie captured method as above.
If you truly can't bear them, a single assassin snail will eventually work his/her way through them.