bristle worm

I was watching my fowlr tank today and I happened to notice this little guy trying to burrow underneath one of my rocks. I pulled the top and then is just squeeze him into a cup without him touching my fingers. Is it a bristle worm? And if so how do I get rid of them? Are they bad? Thanks everyone.!

Hello guys, I'm afraid I might have bristle worms on my tank. I'm still cycling my first tank and its has no fish yet. I've add 15 pounds of live rock and live sand a month ago. And I've seen a few pests such as majano anemoes that I've tried to remove. But today I saw something that looked like...

Unsure if these are French in origin endulging on some escargot , but I as one who loves their CUC does not appreciate it. His friends are just standing idly by as though they're waiting their turn. :(

Hoping I don't have to remove this rock, a pistol shrimp and his goby friend made a home under it.