The black thing that`s encrusting the cabbage coral at the top.Sponge Bob or coral?Before anyone jumps my case the cyano on the bottom left is practically gone thanks to advice I`ve gotten here.Thanks.
It does indeed look like a sponge. I have some of this, it creeps at a fast rate and doesn't care about the light. It actually forced some of my frilly mushrooms to release and float around the tank as it was competing with them for space. Just trim it back with scissors whenever it reaches too far.
