White fuzzy growth. ID?

[Calmbeast]

Hello, I just noticed this white almost fuzzy looking growth in one of my rocks. There were no lights on the tank for a couple months. Now that I have lights hooked up this popped out at me. It looks like it has an opening in the middle. Could it just be a big sponge? Thanks for any help!

 

[760mason]

sponge

 

[cloak]

It's probably just some type of sponge like you said. I wouldn't worry about it too much.

 

[Calmbeast]

Okay cool. Thanks! I get a decent amount of sponges usually.