The bristlenose plecos (Ancistrus sp.) are the most common algae cleaners in the aquarium trade, and they are very cool fish in my opinion. The adult males will grow big "mustaches" on their face. I'm not entirely sure exactly why they grow these, but they don't seem to serve a purpose, so I would assume that they are ornaments used to attract females to mate with them.
My biggest male decided to come out of his cave for a little while today, so I got a pretty nice shot of him. I think he has a pretty impressive mustache, and it surely seem to do wonders for the female bristlenoses in the tank.