This story really does not affect my tank but it is interesting. One day I was wiping some algae off the rock and I found something amazing a colony of sponges that were actually living under the algae. I then came up with the idea that the sponge relied on the algae to give it shade since it was close to my lights. It took me a couple hours but then I realized that the relationship was mutualism because the sponges toxins would make any potential predator think twice before eating the sponge. Besides the fact that my theory was proved today when I noticed that the sponge had vanished from the rock I also found out that this wasn't a fluke and that more sponges were doing this;I knew this because I knew what to look for. Has any one else heard or seen this?