I have a butterfly plecostomus in one of my angel tanks. Unlike some of its larger cousins, this fish hasn't grown very quickly or become very large. It is currently about six inches long and could grow to a maximum length of only seven inches.
It has a suction-like mouth and adheres itself to the sides of the tank, cleaning any algae it finds. It is also a bottom-feeder who sifts through the gravel looking for bits and pieces of food that the other fish didn't get.
I feed this pleco (Big Lips Houlihan) sinking shrimp pellets almost every day. At least once or twice a week, she gets an algae wafer. And I also have a slow release pleco block which includes wood and plankton. Plecos need wood for their digestive system. The white specs on its head in this picture is from the pleco block it had just finished eating.