I have a large mystery snail he's a great vacuum for my tanks and fun to watch mysteries come in a few different colors the ones I know of are black, gold, albino which actually has a black shell, and blue they have white shells. They do a great job cleaning up and are kind of mesmerizing to watch mine learned to eat food from the surface and I've seen him just kind of floating around like a magic carpet Haha. It's really weird to watch them go to the surface for air especially if they have there air syphon fully extended. The only thing with these guys is once they get to around two inches I wouldn't want them in a tank with small fish mine has killed a couple guppies until I placed him in a different tank. Good thing about snails is if you have multiple tanks you can just place them in a different tank from time to time or whenever you feel the tanks need a little custodial work.