Oto cats are really great algae eaters. They stay small, are totally peaceful, and are really cute little fish. They are completely herbiverous, they won't scavenge for scraps of leftover food in the bottom of your tank so make sure you have enough algae for them to eat or they will starve to death (please don't ask how I know this...I am ashamed

). Feed sinking algae pellets, grow your own algae garden on rocks outside in a dish of declorinated water, or hang a piece of veggie like a zuchinni <sp?> in the tank if you don't have enough algae.