I'd like to pass on an anecdote about one of my sponges. It is a yellow encrusting type that had been in my tank for about six months. Everything was going well with it, retaining color and had anchored to a rock. One morning, I was shocked to see it floating at the surface of the tank. I tried to gently press the gas out of it, knowing that I could be ruining its inner structure. Large bubbles came out from where it had anchored to the rock. Now. it is no longer buoyant. The next day, it's floating at the surface again. Instead of removing it, I decided to leave it in the tank. After a few days, it had decayed, resembling a grey cotton ball and settled on a rock. A few days later, it started to encrust on the rock! A couple of days later, it started to turn light yellow! As of this morning, it had encrusted about two inches and is a very pale yellow.
