Ghost shrimp would probably be your best choice, then. They add little to the bio load unlike many common cleaners, can get food particles out of the substrate easily, are cheap, and will eat a variety of foods--clean up from the other fish, undigested foods, and even a bit of algae. A herd or 8 or 9 will be fine, just make sure they have some nice hidey-holes to escape from the fish during their molt. Your fish may be a little attentive at first, but shouldn't cause any problems.