Brittle or Micro Brittle?

i was just taking a long hard look into my rock work yesterday and i saw some tentacles hanging out of a hole in the rock. looks like i figured out what it is! he hasn't come out yet but I'm hoping i get a good look before he disappears

 

I've been trying to find that one or another since then and I've not spotted any more. I'm sure that are 100's of living creatures (pods and such) that I never see in my tank that's part of he cool thing of owning a saltwater tank is the diversity of life.