Any idea what this is?

[fencer]

I actually think I have one of those in the tank. But mine is red

[midgetwaiter]

Originally Posted by Johnny Reefer

Scolymia vitiensis? Pg 132 of Sprung's reference guide. Looks similar.

Based on size aand shape Scolymia vitiensis seems the most likely candidate. You would expect Australomussa to have more than one center in a specimen that size but I did see one about 6 months ago that didn't so you could be right. It is almost impossible to tell these two apart.