Newbie with a hitchhiker

[gnibbets]

I got my first tank set up about a week ago and just found this little creature poking out of the live rock. Any idea what it is and whether it’s safe to keep in the tank? Thank you!

 

[brmreefer]

Looks like a bristleworm. Good CUC. ;Happy

 

[gnibbets]

Thanks! I found another much smaller bristleworm in the tank that was easy to identify. When I saw this thicker one (about 4mm diameter) I instantly assumed it was a slug of some sorts, but now I can see how it would be a bristleworm. Thanks for the help!