Bad worm?

This fella came in as a hitchhiker on my live rock. The tank's been up and running since August, but he's only shown himself in the last two or three weeks. He has to be six to eight inches in total. I've never seen the whole thing, but he'll pop out of a hole in the live rock to graze on the sargassum elegans, which also hitched a ride into my tank. I've twice seen him pulling a leaf off the sargassum and going back into his hole with it in his mouth.

I've read that bristleworms are beneficial, but I'm going to be adding corals, and I don't want him to stay if he might nibble on them. Also, I have to say that he simply freaks me out. Ugly.....

 

they definitely are ugly. ive never had a problem with a worm doin anything to a coral. also i had a large one like that , he ended up makin its way into my sump by himself.

 

Thanks for the reply. He is an ugly thing....reminds me of a snake, and I definitely have a phobia about them. I'll leave him be for now. He hasn't messed with the one coral that I have at this point, so he'll be on probation for now!