Whyis my tank cloudy?

[FragIt Dan]

I'm under the impression Ca precipitates out under insufficient buffering capacity due to a shift in pH, which is low dKh, not high dKh (although I could be wrong). I have seen this happen in a friend's badly neglected tank but it was more like it was snowing rather than a cloudiness. It also caused a complete tank crash.

I have had cloudiness in various tanks many times, ranging from a bit of a haze right up to a look of skim milk. I haven't always been able to track down what was spawning, but I have seen some of my macro algae melt after the water clears up, indication it may have been the culprit in at least one situation. I was quick to test water parameters the first few times and everything was normal, so now I don't bother anymore. Keep an eye on your skimate... if it is any different than normal it may point to the cloudiness being spawn (protein based) rather than Ca. Just my $0.02 ,
Dan