I love my snails...The pomacea bridgesii (mystery snail) is a nice peaceful creature and wont mow down planted tanks...There are some incredibly beautiful colour variants out there now from ivory to pinks, purples, blues etc....They eat a fair bit of crud and produce "infusoria" via their digestive systems...Great for fry..They do poop, but it is easy to vaccuum up, much easier then scrubbing algae off of walls...
I also keep a pomacea canaliculata (true apple snail) They get big anywhere from tennis ball to basball and will mow down a planted tank in no time flat...However, they are also a fascinating species...Very active and curious...
If you dont have a planted tank, or nippy fish that may hurt the snails tentacles, I would suggest try a Cana...
The nice thing about both is they are not hermaphroditic, you need a male and a female to reproduce... If you have more then one snail, you may get a breeding pair, but eggs are laid in clutches above the water line and very easy to remove...