need more info. How much has it shrunk and how long it been going on? Tank params and specs would help. and did you change or add anything to the system recently?
what is your alk, mag and calc at? both alk and calcium can affect the coral, especially if you have had any swings in it lately. How long have you had the coral?
I guess I need to get am alc/ calc kit. I have Ai sol, and Mp10, but they haven't changed for months, and I have and the coral for about 3 months. The tank is about year and a half old.
Get yourself a good test kit. You will have trouble even keeping zoas if you have no idea what your big three are. Red sea and salifert kits are both very accurate and easy to read.