PH Swing(not chasing it).

[boostd2valve]

Hello all, just wanted to get some opinions here about the swing of my ph.  It’s seems to swing a lot but is very consistent. I have done nothing to change it and everything in my tank is doing just fine.   With my apex it goes from 8.09-7.6 during the light off period.  Everyone was out of the house 2 times this summer for a week each time and it went to 8.2x to 7.8x.  I’m figuring it was due to the co2 and being in a newer home.  Should I try to help that number or act like I didn’t see the change?  

[blasterman]

Yep...it's almost certainly CO2.

 

One trick to prove this is fill a small glass with tank water and set it outside for a hours. If the pH in the glass ends up higher than your tank during the day you have elevated indoors pH.

 

Water  / aquariums absorb CO2 like  magnet but don't give it up so easily. 

 

Is it a problem? Sometimes. Low daytime pH does slow coral growth, but soft corals can adapt to it. It's mostly hard corals like acropora that really have issues.  If you have a skimmer running the airline to a point outdoors or next to an open window can really help.

[M. Tournesol]

It's normal. In nature, the sea also have PH swing.

Since at night corals and algae don't produce oxygen, the level of CO2 goes up. This is why refugium is generally put in reverse daylight to compensate for the oxygen drop during the night and thus fight Ph swing.

[M. Tournesol]

You should act like you didn’t see the change.