http://www.guppylog.com/story/2005/6/8/172949/3641
http://naturalaquariums.com/inverts/snails.html

MollieGuppy mentioned the genus Lymnaea in another recent discussion on snails. I was really grateful for that because they used to be present in the millions in a several acre vernal pool/swamp near my home. When we ambled/ waded through there as students, we concluded that there was nothing in that body of water (short of microscopic stuff) which was more numerous. That genus is common in North America and Europe. I would be surprised if they were not also found several places in Asia, though maybe in cooler areas.

I have long beaten the drum for keeping a few pond snails. (I especially like the red ramshorn sport and the more interestly patterned Physa, just as a matter of attractiveness.) I feel that they do a good job of cleaning up uneaten food and sometimes preventing disease. Because they metabolize uneaten food they are not proof against ammonia problems though.

If they multiply like crazy, that is an indication that we are over feeding. We (I, you, whoever) will need to be more careful, step up water changes and take a lot of the snails out of the aquarium at that point. That is work, but a lot less heart break than an epidemic. (Overfeeding brine shrimp in most any form - live baby, froxen, even in flakes - is a recipe for an outbreak of velvet.)

I'm in the process of tearing down a long established livebearer tank that is pretty dirty and over run with plants and snails. The darters will get the snails, the better plants will be returned to that and other tanks. A lot of plant and snail shell debris will hit the compost heap. And I'm agonizing over which of the fish which would do wonderfully well in there, will get promoted to that aquarium.