Mystery pest ID help

[GillsGoneWild]

Found an uninvited guest crawling on my gorgonian this morning. Tried sucking him up with the turkey baster but the little bugger is quick. Pulled the gorgonian out in order to get to this critter and was surprised when this thing actually swam to the bottom of the container I put him in.
It's approximately 1/2" long. Any idea what it is?

 

[Triggerfish]

fire worm?

 

[GillsGoneWild]

fire worm?

I don't know; doesn't look like any fireworm I've ever seen before.

 

[Triggerfish]

are the bristols white? cant really tell/.

 

[GillsGoneWild]

are the bristols white? cant really tell/.

No, same color as the rest of the body. At least as far as my color blindness allows me to discern.