I have a ~3 inch long pygmy angel that has been in for around 6 months. I have pulsing xenia, leather corals, zoos, star polyps, and a few other "not sure" items that have been safe from him. I do see him picking at algae at some times, but not much.
He was aggressive at first to my niger trigger when introduced (roughly same size), but does not bother the other inhabitants (false percula, bar goby, banggai cardinal, yellow chromis, etc). He gets along well with others in my 60 gallon.
He did take out a peppermint shrimp today within 2 hours of placing the shrimp into the tank though. I was not aware that may be an issue and will see if the other peppermint guy makes it. They are very small @ $3.00 each.