Looks like some type of leather. Does it have a skeleton structure like acropora or is it soft ?? If it was a type of acro you would be able to snap branches off. I am going with it is a sponge
No like I said it is soft but grows like acropora. No hole at top of each branch but I am thinking sponge too. Growing like crazy. Hope I can control it if it gets too big. Anything eat sponge but yet generally reef safe?