Someone talk me out of this (choco. chip star vs. mushrooms)

[Ivy]

Uh, whoops? Brittle stars eat corals?

I just bought a rock with mushrooms and it came with 2 hitch hikers, a banded shrimp and what I think is a black brittle star. I haven't quite seen it, but legs come out of the rock and wave at me.
Should I panic?

Ivy