Is this a harmless sponge?

[JohnNYC8]

I just dipped a green hairy mushroom and it attached itself to some egg crate so I don’t want to remove that. Is this some harmless sponge in the corners or something I should be concerned about?

 

[SnazzyUrchin792]

No idea if it’s harmful or not, but the one I have like that has never bothered anything yet. Fairly slow growing.

 

[JohnNYC8]

No idea if it’s harmful or not, but the one I have like that has never bothered anything yet. Fairly slow growing.

Hmm I could easily use a scalpel to remove it now…