basic question, why ph swings for night and day?

[fungia]

hi. i have a basic question. i know ph is higher during the day and lower at night, although i never found out why. anyone want to clue me in? tia!

 

[Len]

It pretty much has to do with biological processes, namely photosynthesis during the day (oxygen byproduct) and respiration at night (oxygen consumption, CO2 byproduct).

 

[Unarce]

You can tighten the swing with a lighted refugium with macro at a reverse photoperiod. It will keep dissolved oxygen constant in the water by continually removing nitrogen and phosphorus during the main displays dark cycle. The refugium has other benefits as well. :wink:

 

[ChrisRD]

I have my auto kalkwasser topoff only run at night. That keeps the pH range pretty steady for me (about 0.10 to 0.12 swing).

Running a skimmer also helps keep pH stable and in a good range IME (helps off-gas excess CO2).

I've not had much luck with the lighted refugium thing - didn't get much of an effect on system pH from that. Maybe it just wasn't large enough (about 20% the size of the main tank).

 

[Anonymous]

hi. i have a basic question. i know ph is higher during the day and lower at night, although i never found out why. anyone want to clue me in? tia!

From what I hear ph lowers when carbon dioxide increases. With active plant life consuming carbon dioxide during lights on, the carbon dioxide lowers and ph rises. vice versa at night.

 

[badgergoth]

When your carbon dioxide levels rise (i.e. at night when photosynthesis is no longer occuring) more carbonic acid is produced, so in effect there are more hydrogen ions in solution.

http://en.wikipedia.org/wiki/Carbonic_acid

pH is inversely proportional to the number of free hydrogen ions are in solution. acid (lower pH) = more, basic (higher pH)= less.