I dont think it's harmful
we got it at the local fish store for 3 bucks.
the guy said they are good sand sifters.
i just wanted to come here and double check since we all know how much the LFS people know somtimes.
he/she/it will crawl around the sand for a bit then tunnels all the way under and stick his little tube out of the sand as it moves around. Then comes up and digs down in another place.
thanks