Growth on Hammer coral

[Nathan73]

Hey Guys,
I have a green wall hammer that’s been in my tank for about 5 months, and has been doing great.
last night after lights went out and it closed up I noticed a white growth on one side and have no idea what it could be.
the coral opens, is really puffy and happy looking so I don’t think it’s affecting it but would just like to know what it is
Thanks

 

[MaxTremors]

Could be a sponge or even a tunicate, but would need a clearer picture.