Is this a bristle worm?

[Mystichrome]

Found one of these in my tank this morning. I managed to catch it and remove it anyway to be safe but just curious

 

[paulsz]

yup that's a bristleworm. Harmless. If they poke you, it hurts a bit, but nothing to worry about. Your tank probably has a few of them. They eat detritus and are part of the clean up crew, so they are good guys. They are ugly and creepy, but try to get used to them, because it'll be very tough to get rid of all of them. I started out with a few and after a few months there's a TON of them. They mostly come out at night. 

 

Also, you'll see them sitting on coral and frag plugs (mostly at night). It hasn't hurt any of my corals yet, so i don't think it's anything to worry about.