Can somebody ID this?

[JDF24]

I recently moved some of my live rock around and then noticed two little pieces came off and had this stuff all over them and even a little bit on the main rock. I don't know if this is some kind of algae or something else and if it's good or bad. Does anybody know?

 

[saltyfilmfolks]

looks like sponge.

 

[AnOldSaltyDog]

+1 for sponge

 

[Aliu]

Agree with the other comments. Harmless sponge

 

[Diesel]

Kinda looks like to me dead hair algae.
But what ever it is it's harmless.