Mystery Snails
Survive in aquariums: Yes
Survive in warm ponds: Yes
Survive in cold ponds: No
Plant eating capacity: Low to High (varies with species)
Algae eating capacity: Moderate to High
Breathing: Gilled
Breeding: Sexual, egg-laying; some people say that some are live-bearing
In most cases, mystery snails are apple snails so see that section as well.
Mystery snails are medium-sized tropical snails. Some mystery snails are Ampullaria sp. such as the four horned and Golden Inca snails above which are heavy algae and plant eaters. Another keeper of apple and mystery snails says that all mystery snails are the apple snail, Pomacea bridgesii (usually written incorrectly as Pomacea bridgesi). Yet another source says they are all Pomacea cuprina! The guy who runs applesnail.net says most mystery snails are Pomacea bridgesii or from the Viviparidae family. I have seen snails sold as mystery snails that are all different colors and obviously multiple species. There is no agreement between stores, keepers, and "experts" as to what is what. Some mystery snails eat algae and detritus and do not overly harm plants. Since they must be kept above 70 degrees F at all times, they cannot be kept in ponds except in tropical regions.
copied from:
http://www.fishpondinfo.com/snail2.htm#mystery