What is the Ph of the tank? It would extremely difficult to keep your Ph at even 7.6 Ph with Nitrates that high. How long has the Alveopora been in the tank? What other corals do you have in the tank?
Give us more info on the tank like system volume, filtration, lighting, flow, stocking levels ( I assume with NO3 that high you must have a lot of fish), and most important other parameters like PO4, Kh, etc. and maybe some Pics.