I agree with Todd. It is most likely Garra rufa. They have been imported in the past few years and used in spas. People get into a spa filled with these fish and the fish peck at their skin. They are also known as doctor fish. Their are companies that sell the spas and the fish. Fishbase says the adults get to 14cm so that would be about 5 1/2" - 6". There is another species, Garra flavrata that is sold under the name of Panda Garra. When I worked for Tony's Tropical Fish in York before he closed we sold a lot of these as well as the rufa. They are from Myanmar. The flavrata have a banded pattern, hence the name panda. I'm not sure but the could lose that pattern once the get to adult size. If your fish has any red coloration in it's caudal fin it could be flavrata. Both fish are recent imports within the last 6 - 8 years.