What you described is definitely a Chinese Algae eater and I agree...take him back to the store. I bought one for my 10g (didnt know about them) and he was fine for a while, cleaned all the brown algae from my tank, but then he stopped eating algae and would feed on the algae wafers I throw in for my cories. Then one day during my routine gazing into the tank I saw him swim up really fast to my gourami and attached himself. The gourami quickly shook him off and swam away. I only saw this once but that was enough. HE was outta there! The lfs wont take him back so I gave him to a friend with a much larger aquarium than mine. He's doing better in there. Get rid of yours before its too late.