Hi all,
As the others have said Red Ramshorn (Planorbis corneus), they are mainly plant safe and great for maintenance, and I have them in all my tanks where the water is hard enough for them. There only down side is that they can become numerous enough to keep shrimps off their vegetables. As well as Puffers and Loaches, If you crush them they are a favoured food for Dwarf cichlids etc.
cheers Darrel