Help Identify - Coral

[Fish Dad]

Hello all - Can you help me identify this.

I have no idea never bough it, was just floating through the tank one day though it was a bright green paly.
Put it in its current spot and now after months it is about size of nickle? but no new heads have formed?

Kind of thinking is not a Paly.... Bright green with yelllow green center.



Couple pic - one open and one of it eating - loves to grab food when feeding the fish...