Name that Creature

I finally saw it again - thought I was going crazy. There's a very small creature living in my button polyps -- I tried to take a picture, but zoom isn't strong enough.

From what I could see (with the aide of a magnifying glass and flashlight), it looks like it might be some type of mini brittle star. It's body appears to be a small black disc, with long, black and white banded arms. The first time I spotted it, I thought it might be some kind of worm, but it's not. I think the button polyp is it's home - have never seen it roaming about.

Any ideas? Haven't looked up in the picture books yet. Thought one of you guys might know right off the top.

Thanks!

 

Thats what it is a mini brittle star we have millions of them i the systems at work and I have them in my fuge and entire system good to have. It came in on rock or sand or as larva in water ? It all arrives sooner or later

 

It's very cool looking. It was kinda creepy, until I figured out what it was.