need help identifying

[neocamden]

We have been watching this grow for the last 6 weeks. It has a ridge line running on the top (in the photo it goes from left to right. It appears "fuzzy". Any clues would be helpful

 

[Fluff]

Looks like a sponge.

 

[roka64]

I agree.

 

[neocamden]

thank you both for your input. It has been fun spotting it, then watching it grow

 

[melosu58]

I agree, a sponge.