The bigger tank you can get, the better. The smallest tank I'd keep one in is a 33g tank, but this will really limit what you can put in there. I myself have a chinese algae eater in a 35g tank with an assortment of barbs. The barbs are too fast for the chinese algae eater to bother. I'd recommend a 55g+ tank; with more space the fish will be less aggressive and territorial and you'll also have more of a selection of companions.