Dead fish, missing anemone and nitrate spike

[dsaundry]

You need to do a lot more than a 12% water change. I would be doing 200% over 12 hrs.

I wouldn't advise this as it might be too much of a change too quickly for your system. You could actually cause more stress to the system. As far as the cloudiness goes, 2 questions, do you have any anemone's in your tank?? If so are any missing? Do you use activated carbon in your system?? If not I would set up a carbon reactor and this should help clear your water up and remove some of the toxins that may be in it.