I'm on the sponge is bad side of the fence. Sorry! I have all types of it. It has choked out many a zoa and some LPS. And limits where I can put corals. Nice clean rocks are my favorite thing, since I like corals better than sponge. I do have one exception. A beautiful orange sponge I have growing on a very large rock that is the centerpiece of my 65g tank in Utah. I treat it just like any other coral, give it a bit of space and hope it grows bigger.

The grey, pink, and yellow are the most annoying. Pull off what you can. I also gently use a toothpick or soft toothbrush to clean it out of corals, but it usually comes back. I only do that on the ones I can take out of the tank though. I also put rocks on top of it and then the corals on top of those rocks to make it easier to take them in and out for maintenance.

I have tried exposure to air, the freshwater dip. Doesn't die!