Cloudy water in the morning only?
I know many people have asked similar questions many times. But I can't find a reason for my specific problem so bear with me, please.
There is a medium sized tank, well established, well planted with good growth, moderate fishload with no overfeeding, Co2, big biofilter, no suspicious water parameters, no sicknesses, no nothing. On first, and second, sight everything's perfect.
But on more days than not the water is slightly cloudy (white, no particles) when the lights come on. It gets better as the day goes on, after around four or five hours the water will get clear, shortly before lights off it's short of crystal clear. The next day again the milky imperfection...
This cloudyness also persists after weekly waterchange for at least a whole day.
No cloudyness after fertilizing. No change if the night before the fish had no feeding.
I wonder what can be the reason for this strange behaviour of the tank's water?