The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
The use of the words "serpent" or "brittle" are hobbyist designations and really not an accurate means of identification. The image is not defined enough to determine much. Could be Ophioderma sp., Ophiolepsis sp., or Ophiocoma sp.
Looks like a mini brittle star to me. The kind that hang out in the live rock and you almost never see more than a tentacle or two. Certainly nothing to worry about either way. Nice shot sdellin.