What is this flower like entity growing on the live rocks?

[Gore15]

During a nightly inspection I came across 3 of this entities. They open their petals (like a flower would open) and close on light change. For example if I shine a phone flash light on it it can close or open so light change make it react. I could not make a better photo but will try.

 

My main suspicion is Aiptasia but it looks much smaller and I could not figure out if Aiptasia reacts to light like these ones are doing. If you can give any suggestion on what this is, please let me know.

[Jungle_v_i_p]

Small species of feather duster or tube worm. Harmless and beneficial filter feeding rock hitchhiker. Really common. Congrats! Lol

[Tired]

Yep, tubeworm. They retract when startled, and can be startled by light changes. 

[Gore15]

I wonder if this is going to grow big or they stay small?

[Jungle_v_i_p]

It will stay small. Won’t get much bigger than it is stay the same.