American Flag fish, Mollies, Platys, Swordtails... all known to eat algae of
various types. Flags will take care of hair algae in my experience. They
will graze on that stuff like crazy. Mollies take care of thread algae
growing on old plant leaves. Platys and Swordtails aren't all that great but
they do eat SOME algae here and there. American Flag male would be a little
territorial at first but should settle down after a couple of weeks of
defending a territory he's claimed. Females don't do this but they aren't
1/2 as pretty as the males. AFF are actually a type of Killie fish just in
case you were wondering. People often use them in ponds as they are very
hardy and readily breed in the right conditions. Plecos usually eat only the
flat algae that grows on glass, wood and rocks. In my experience AFF are the
best of the bunch for taking care of algae. At one time their breeding tank
was the only tank I had that wasn't infested with some sort of algae or
another.