Hi all, I think I am having my first encounter with STN in one of my acros. My urchin keeps ripping it off the rock and dropping it all the way down my rock work and I believe this triggered it. It happened about 4 times and for now I decided to reglue the acro and banish my urchin to the sump until it can encrust. Anyway, here is a photo. As you can see, the right side is turning white. If it is indeed STN, what can I do to stop it? All of my other acros are doing well, colored up and extended. I don’t think it’s necessary since it is just on one frag but if you all want params I will check them.