What is this thing ?

[Michaelb406]

I have had my tank setup since September 15. I was changing my rock around a bit and saw this worm looking creature. I started with Caribbean Sea base rock totally bleach white. I have added some hermit crabs and fish but no live rock at all could this thing have hitched a ride with a crab or snail ?

 

[AbsoluteFaye]

Bristle worm. Good for your clean up crew. Bad if you touch it! Has bristles like a cactus.