Any Idea what these arms are under my rock?

[lowlow411]

 

[Paul B]

I forgot what they are called but any healthy tank will have thousands of them. I have them coming out of any crevace in my rocks and have been there for decades. They won't harm anything.

 

[Dburr1014]

Brittle stars. Most likely the small kind that are considered part of clean up crew.

 

[Chrisv.]

Agreed, the little micro brittle stars. Free cleanup crew!