the great ramshorn snail ( planorbarius corneus) is a large native ramshorn species growing to around 3 cm ,they are great algae grazers and will eat algae from rocks, glass and plants ( they wont eat live plants ) aswell as scavenging detritus fish waste ,dead fish and left over fishfood  ,being a native species it can survive uk winters but can also be kept in coldwater and tropical aquariums ,snails make up an essential part of a pond or aquarium ecosystem and would make an excellent addition to a wildlife pond.