[Birdman]

I'm having problems with the water in my QT tank. It's 600 gal, flow goes from bottom drain to fluid bed filter, then back to tank via a pondmaster 950 pump. I am keeping the tank covered with clear skylight poly to try and hold as much heat in it as I can. I am heating it with 1000 watts and trying to keep the temp. in the 70s for QTing my new fish.
Problem, my water keeps turning cloudy, dosn't stay clear. It will cloud up to the point you can't see the fish in about 2 days. If I turn on my flow through that will clear the water but then the temp goes down. Flow through is from well water. My PH is 8.2, Ammonia, nitrites, and nitrates 0. But my test kit I know is out of date. Would ammonia make the water cloudy? Any other ideas?