Help Identifying!

[Coral*Beauty]

I just noticed a worm looking thing in one of my rocks! It came out to get a piece of food that was on my sand, its pretty long! Can anyone identify this thing and let me know if I should be concerned?!

Thanks reefers :)

 

[Lionfish Lair]

It's just a common Bristleworm. Good guy. He's cleaning up your mess. :-)