I've recently had some calcium issues in my tank. It shot up to 600 ppm as I reduced my alk levels. I want to try to keep them closer to 7-8 dkh for the very reason that high levels seem to demand higher calcium dosing. Before anyone asks, yes I have ordered another Ca test kit and will compare when I get it. Would tis fluctuation bring on STN, or should I be looking for other causes? If so, what? Here is the affected acropora. It has bleached and has STN around the base. What can I do?