Could somebody please ID this thing on my LR?
It started kind of small but is now about 3/4 inch deep and 1/2 in wide. It has a small hole in the middle of it. I've been trying to locate something inside, but with no luck.
I have a TON of corraline on my rocks. They're almost completely purple. The weird thing is that my water parameters are completely out of wack right now too!