Xenia quesion

Actually, it is the light. I moved it to the back of the tank. And the light is different. I did my weekly water change and did notice that it has attached to the rock i put it by and there are a couple new ones also.

As for the alkalinity, I don't know that off hand. I have the lfs check it for me every other week. I don't have the proper test kit.
I rip it off the rocks and dump it into my sump. the only way to control it is to let other coral cover the rocks. I've had luck with zoas and palys blocking the zani from growing. All I really have to do is pick off a little here and there. The only other way I found was to let it grow upwards. It will grow up the glass and overflow and become easy to pick off without leaving pieces behind. slowly im eliminating it.