Does anyone know what this is?

[Phishguy3.0]

So I’ve found this growth on the underside of a rock in my tank. Before I pull the rick out and rinse it off I’d like to know what this is. Any help is much appreciated. Thanks!!

 

[Dragon52]

If your talking about the white stuff looks like sponge to me, harmless filter feeder.

 

[NISMO703]

Looks like some kind of sponge to me.