Does this worm you are trying to ID have like lit ewhite hairs on its sides?
kinda a dul redish coloring half way and dulwhite the rest?
I couldnt open the pic forsome reason that was posted..
but yeah those are fine.. they wont hurt anything.
mine crawls all over my zooanthids eating stuff off the rock and the zoo's dont even mind him there. and none have came up missing or chomped on..
but like was said... try not to grab them or touch them really cause they do pack a bit of a sting!
one other thing..
I've read that they are wonderful for eatthing waste in you CC or sand bed. and the more you have the better..
So on day i caught one with a pair of plastic tweesers.. and i chopped him in 4

not only did he regrow but now there are alot more so i think they may be reproducing

my CC is filled with them.