Hitchhiker in a hole. ID please.

[Nano Saltyy]

I bought some live rock for bacterial diversity in my tank. It seems I got some interesting hitchhiker in my tank.
Please help me ID this one.
Also is this a beneficial hitchhiker or a bad one?

 

[kittenbritches]

Do you have a photo?

 

[elysics]

Maybe a peanut worm, hard to tell, can barely see anything in that video

 

[Isopod80]

Peanut worm is a reasonable guess. (If so-harmless) Definitely seems to be a worm of some kind. There's just not enough there for a definitive i.d.

 

[GzO]

Similar? But two that extend from single growth.

 

[KJ]

I bought some live rock for bacterial diversity in my tank. It seems I got some interesting hitchhiker in my tank.
Please help me ID this one.
Also is this a beneficial hitchhiker or a bad one?

Peanut worm harmless