sponge or not

[DonDon1]

Can someone identify this stuff between the two pices of rock. It is sponge like and grew from dime size to 4 inches in 5 months. Originally it was just on the bottom of the top rock when I bought a piece of galaxea. It has fused the the two rocks together.

 

[Kreeger1]

can't see anything in that pic. Could you possibly get a clear picture?

 

[itZme]

I have some stuff that looks just like that. It is some type of sponge. If you could get better pics we could verify it but I am just guessing from the blurry pic. The holes in it look like the the ones in the sponge I have on some rocks. It is very bland looking and blends in with the rock pretty well.