Pterygoplichthys gibbiceps, grows about 18 inches long and regularly hits 12 inches in aquariums. Feeds on algae, driftwood and dead fish and shrimp. Make sure there is driftwood in the tank and do a 75% water change and gravel clean the substrate at least once a week. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Be careful if you have to treat the tank for anything. They are sensitive to chemicals.