What is this?

[BRCREEF]

Hello I was looking at my tank and saw this growing. I have never seen this stuff. My tank is 1 year old.

 

[Ron Reefman]

Hello I was looking at my tank and saw this growing. I have never seen this stuff. My tank is 1 year old.

If I had to guess, I'd say it's a sponge, but I'm not sure. I see some that look like that when we snorkel in the Florida Keys.