The best poop eater is actually the bacteria in your tank.
Now if you want to clean your tank regularly that is the best thing to do. Sorry to say, there is no magical fish for jobs like this. Normally its mother nature but your tank is just to small to do all that without your help. I would start by buying a python or any hose and just start doing weekly water changes. This should clean your tank better than any fish.
The same goes with Alage on your tank. No great alage eater, just gotta get a blade and start scraping the sides.