Oto's are a small type of catfish. They do a great job at cleaning up algae when used in groups. They get along well with about any kind of non-agressive fish. They are easy to take care and fairly hardy. I should mention, that if you are planning on buying some, be warned that they have a strange way of dying when transported to a new tank. However, if they last for a week or so after you put them in your tank, they will probably last you a long, long time. Make sure your LFS has a decent warranty!