Sorry to reply to an old post but I think it's better to keep experienceces all together
Yesterday I've received a collospongia. I put it in a small picoreef.
Then looking for infos I've read this discussion and decided to try to put the collospongia in my other aquarium that have red slime (cyano) growing in a corner and ciano+dino on the back and side glass.
Made this yesterday evening, and no other changes.
This morning the red slime patch is disappeared! O.o
And the walls seems more clean without cyano bubbles.
What makes me sad is that yesterday I didn't took a picture because, to be honest, I didn't think it could be true and effective.
I want to try to remove the sponge and see if the slime grows back again.