what about a big apple snail. i have some with my devils and they dont even get noticed, i use them in all my tanks. mine are about tennis ball size though, they cant eat it whole so they ignore them. great for finding food that gets stuck in the no flow areas of my tank. but overall they will just make the tank dirtier. they poop alot. do nothing for the glass/algae. usually sell for 6 bucks in a store at this size.