Help ID this

[Pola0502ds]

What is the white stuff growing on this? The picture is or my pump from skimmer but this stuff is growing all over anything in my sump. Is it good or bad? Keep it, remove it?

 

[RMS18]

Sponge not sure of the kind but I have the same one growing on zoas. I have hit it with peroxide but it grows right back. Kinda reminds me of a bird nest coral.

 

[Pola0502ds]

Thanks!