White Cacoon like Membrane between rocks

[shaggy1902]

Hello everyone.

Have a 120 gallon that's been running for almost 2 years now

I have this weird white membrane that has been growing larger for several months

It's become this Cacoon like membrane structure and I'm wondering what in earth it can be. This tank was started with all dry rock. I hace lps and fish in the tank.

Appreciate your help!

 

[shaggy1902]

Hello everyone.

Have a 120 gallon that's been running for almost 2 years now

I have this weird white membrane that has been growing larger for several months

It's become this Cacoon like membrane structure and I'm wondering what in earth it can be. This tank was started with all dry rock. I hace lps and fish in the tank.

Appreciate your help!

It also appears to be between 2 hard rock surfaces. Like the bottom part is a thin piece of rock. It's really odd. Almost like a clam on the bottom half of the thing.

 

[EeyoreIsMySpiritAnimal]

It looks like a sponge.