I have what I think are keyhole limpets growing like crazy in my tank. They seem to keep the algae at bay and don't seem to harm anything. There are sooo many of them. Does anyone know much about them? Should I consider trading them for something else, since my tank is a factory of them? Any info or suggestions are appreciated. Thanks. The photo below just shows an example of what mine look like. I can probably get some photos of the ones actually in my tank.