Looks like a sponge?

[ferro]

Is this good or bad? Looks like some sort of sponge to me.

Sorry for the blues... it is white in appearance.

 

[DSC reef]

Looks like sponge. Not harmful but if it takes over it's easily removed.

 

[Lovemyreef2015]

Agreed, sponge

 

[DeepBlueSomething]

+1 sponge

 

[ferro]

Thanks for the replies! Just on the side of one of my rocks 2"X3.5" area. If it's beneficial I'll just leave it! I have tons of feather dusters everywhere and I like letting hitch hikers grow ;Happy