I am pretty certain it's alive and it must be an invertebrate.
I have had a small hole in one of my Fiji rocks. Recently something started growing out of the hole. It grows fast and is now about half an inch protruding from the hole. It looks like a white wafer-thin leaf and is slightly green at the edges, but otherwise complete white. I can't see its base since it is hidden in the hole. It does not move in the water current, so it must be hard/solid.
I have had a small hole in one of my Fiji rocks. Recently something started growing out of the hole. It grows fast and is now about half an inch protruding from the hole. It looks like a white wafer-thin leaf and is slightly green at the edges, but otherwise complete white. I can't see its base since it is hidden in the hole. It does not move in the water current, so it must be hard/solid.

