You really don't NEED an algae eater.
I'd like to bring to your attention the behavior of the Dwarf Cockatoo Apisto. It is advised to keep them in a planted tank(then again, it is always best to keep fish in a planted tank) and to have 1 male to 2 females or 1 male to an entire school of females. In a tank that size, I would keep only 1 male with the rest being females. I've also read that min tank size is 30 gallons.