i have a pair and they seem to be peaceful. I've never caught them picking at corals or killing anything. After I feed my polyps they will come and try to take the food out of the polyp, but never eat the polyps.
i also have a pair of cleaner shrimp, and a pair of red fire shrimp. and about 5 camel shrimps and a few peppermints. they all seem to exist peacefully.
good luck!
jb