Clown Plecos are awsome fish, I just put one in my twenty gallon. But they're a wood eater, not algea eater, although I have yet to see my little guy suck on the driftwood. I swear he's eating algae, but I can't prove it. Mostly he seems to like sucking on the glass and decor. I put an algea wafer in my tank every other day anyway for my other fish, just to round off the diet, so maybe he's eating that *shrug*.
They're great little plecos that don't grow much more than four inches. Usually they're secretive and nocturnal, but I guess I got lucky, mine seems more visual than most. It's only a 1/2 inch in size right now, sooo cute.
Oto's are probably your best bet for algae, and reducing light and nutrient levels, and a little manual scrubbing.
~~Colesea