What might this be?

[Xzibit]

I found something growing on my LR between a crack. It looks semi clear and almost gelatenous and it looks like it has bubbles in it. I will try to get a pic of it up if I can figure out how to post it.http://www.geocities.com/carstan0s/DSC00197.JPG

[benjen]

Well... The picture isn't clear enough to be sure, but it looks a bit like one of the sponges I see in my tank. If it has one obvious hole in it, it's probably a sponge.