Just a note from my expierience:
I used to have black beard, green, stringy and any other type of algae in my 50g bow front tank, I had pretty much given up on the black beard algae after trying ancistrus, amano shrimp even some nasty chemicals in the smaller tank. One day I was in the LFS and saw a curious looking gibbiceps plec, he looked really cool with his flared nostrils and almost star like pattern around his eyes.
Anyway to cut a long story short,after two days in my 50g, the was no trace of any type of algae on plants, bogwood, glass. In fact the bogwood was cleaner than it was after I gave it a good scrub before putting it in the tank, and is now a permanent shade lighter! Hence his nickname suggested by my girlfreind ' The Gob'
Two things tho:
He gets very big 18" + (but gets cooler looking the bigger he gets!)
He really does crap like no fish I have ever seen! but this is much easier to remove than algae!
see a (bad0 picture of him in my post in the aquarium pictures gallery 'The Gang'
Good Luck!
Ken