pH Changes Over a 24-Hour Period???

[bruinsbro1997]

Just wanted to know if this was true. Got it from a recent book at the library, from 2005-2006 I believe.

During the day
"Carbon dioxide acidifies the water. The plants absorb this for photosynthesis, so the water is less acidic: the pH goes up but stays within the normal values and has no effect on the fish.

At night
"There is no photosynthesis; the plants and fish respire and give off carbon dioxide, therby acidifying the water and lowering the pH value. All these variations are normal."

 

[Mumma.of.two]

I have no proof but, yes, I have heard that if you check you PH in the morning and check it again in the evening it will be different.

 

[Rokuzachi]

I have also read, and experienced that small ph swings happen due to this. I had no idea until I read about it not long ago, and sure enough in my jungle of a tank I checked and there it was.