What are your water parameters still? Have you added anything to the tank lately? How long has it been setup? Has for the naso sorry for the luck but those fish are notorius for just up and dying. How much water did you change last time, and did you notice if it got cloudy after the change or before the water change. I will suggest 3 things I think it is: 1) when you did the water change you could have took to much out and the bacterial colonies are tring to catch back up to what they used to be, 2) algea bloom. This is when the algea is free floating in the water, this is why your getting the milky look. A UV sterilizer will take care of this. if you already dont have one. 3) I noticed you stated you had cruched coral that stuff can be really bad. When distrubed will cloud the water and it will look like a mily kind of water (like your stating). It will do this for a life time. Did you notice any of your fish kicking up the coral lately.fishlady said: