Can anyone identify what this is?

[ScubaGirl]

Found a couple more of these things. I apologize, the first pic is not the greatest (it's in a cave) and I had to use a flashlight making them more yellow than they actually are. The second one is quite different than the others in my tank. The original ones that I posted before all look the same, they haven't changed a bit.

[Wayne]

Those above look like sponges to me Any healthy system will have them.