After changing the total volume of water over a two week period, my 300 gal. reef tank is still cloudy. Really, really, milky white. For no reason, the aquarium cleared up for two days, crystal clear, and has gotten the cloudiest ever. During the cloudiness, the pH drops from it's normal 8.3 to about 7.8. Adding marine buffer brings the pH back up and usually the tank clears up for a few days before dropping the pH and getting cloudy again. CA is 420 and KH is about 109. AM, NO2, NO3, PO3 all 0. Any ideas?