Strange creature in my Marine tank?

its called a bristle worm if u have live rock u prob have many of theses fellas. there good for the tank they shift the sand around. they can get very long though. if u dont like them in ur tank u can get a bristle worm trap from the pet store. also dont try and put ur hand in there and pull it out they sting and it hurts always wear cloves when dealing with these guys. if u have any more questions email me rachael_sax@yahoo.com