Any ideas for identifying please

[Jimbhoy13]

I rearranged rock work in tank today before doing a water change. I removed 3 pieces of rock and about five minutes later I saw movement on one piece. I used tweezers to catch the critter and put it in a cup of tank water. It’s still alive. It’s very small and would fit on my thumbnail. Is it a brittle star? Not added to my tank so must have been there a while. Never seen it before today. Do I keep or ditch?
Also as I changed positions of rocks I noticed the green topped coral(?). Again not seen before. Can anyone identify please?
Thanks.
Jim

 

[xxkenny90xx]

Mini brittle star, I used to have hundreds of them. They're harmless, very cool, and help keep your tank clean.

 

[jsker]

A brittle starfish

The other one is hard to make out. Could you possibly take another picture please

 

[reaper0268]

Brittle starfish are an excellent addition to your cleaning crew.

 

[Auquanut]

^^ What they said. If you ever need any, I've got billions.