Cute little wormy thing in my live rock... Good or bad

[kilofey]

Its black with either white or yellow stripes (only saw it for a second) when it gets scared it retreats and you can see just the tip of its body. Its about the width of .5mm pencil lead that comes in mechanical pencils, not sure how long it is, maybe half inch, I only saw about a quarter inch of it.
I hope its a good thing, cause thats the first bit of life I will have seen in my tank so far lol, no fish yet, just a few pieces of LR

 

[er95]

Is there multiply tentacles? A pic would help lol

 

[kilofey]

I didnt see tentacles, but he has a mouth I think. I wish I could get a pic, or just see him! Lol
Do u know a list of bad worms and maybe I can google pix of them?

 

[er95]

I dont know much of worms, the other day I spotted two baby brittle stars, it was awesome! Thats why I was asking about any tentacles.

 

[bang guy]

Are the stripes along the length of the animal (Nemertean = bad) or across the width (lots of possible suspects, all good).
It's also possible it's the tip of a Brittle Starfish leg (look for a couple more in the area).