What is this

[Reefgazer]

This has grown in my tank just wondering if anyone knows what it is its the polyp in the middle if the tank on the left of the white sponge?

 

[nudibranch]

it looks like aiptasia too me but could be wrong look it up too make sure

 

[Reefgazer]

I don't believe it's aptasia it's not clear like aptasia normally is, I am thinking is it some sort of button polyp, because if the position in the tank this was the best photo I can get but the middle of it is bright green with a brown frilly outer part