Smooth white bump on LR, growing and seperating??

[Ge-off]

I have a white bump on a piece of my LR thats a little bigger then a pea. It is growing slowly and I am seeing some small dark dots inside of it, since the outside is semi transparent. I tried my hardest to take a picture of it but it's just deep enough in my tank where my camera doesn't want to focus on it!
What is this thing??

 

[smnw10]

i have 3 of these on a piece of LR I just recently got and am very interested in what it is as well. My 2 of mine are nickel size and one is almost quarter size.

 

[Zer0]

They are sponges. Harmless filter feeders, that come and go in our saltwater aquariums. Nothing to be worried about, and since they are so on and off, that one might disappear, and then others may show up again.