Good worm, Bad worm?

[67Stang]

While checking out my tank last night I noticed a black worm moving around. In and out between the live rock.

It is at least 2" long, skinny, black and has a pin like head that comes to a point and is lighter in color. It seems to move slowly but when startled it can shoot like a rocket to a hiding place under the rock.

I don't have a camera so taking a picture isn't an option.

Can someone help ID this guy?

Good or Bad?

Thanks

 

[67Stang]

can anyone give me some advice on this before I rip out my rock trying to catch him?

 

[bezzer]

Sounds like a bristle worm to me.
My suggestion would be to leave it.