What the heck is this?

[emmace]

I just started my first reef tank a week ago and used live rock to help jumpstart the cycle. I’ve started seeing a few hitchhikers (including an aiptasia, unfortunately) but found this weird little dude. What is it? The most I could find is a tube worm but I’ve seen others burrowed closer to the bottom of the rock into the sand. I just want to make sure it’s reef safe!

 

[Crabs McJones]

Spionid worm