Brown substance on Zoos?


New member
I just noticed on one of my zoo frags I have had a polyp on the back that wasnt opening. SO i picked it up and looked at the polyp and noticed what looked like a brown substance growing on the polyp. The brown has spread to the base of a few other polyps close to it, they are open and happy though. I can also see where one polyp melted and used to be.

So my question is what should I do?