pH Daily Fluctuations

[Rocky Mountain Reef]

I know that pH can fluctuate during a 24 hour period, but what is acceptable. It is normal to be higher during the day and then drop lower at night. My pH has fluctuated from around 7.8 at the low side during the night to 8.3 during the day. Any thoughts?

 

[Crabs McJones]

Yes, when the lights come on in the display ph will rise, and when lights out ph will drop. the swing really depends on your system. this is why some will put a refugium in the sump and have the lights for the macro algae opposite of the display tank. when the tank lights go out, the fuge lights come on and ph stays pretty consistent

 

[Sophie"s mom]

I know that pH can fluctuate during a 24 hour period, but what is acceptable. It is normal to be higher during the day and then drop lower at night. My pH has fluctuated from around 7.8 at the low side during the night to 8.3 during the day. Any thoughts?

Perfectly normal. PH will drop overnight with lights out, then begin to rise during the daytime.

 

[Rocky Mountain Reef]

Yes, when the lights come on in the display ph will rise, and when lights out ph will drop. the swing really depends on your system. this is why some will put a refugium in the sump and have the lights for the macro algae opposite of the display tank. when the tank lights go out, the fuge lights come on and ph stays pretty consistent

That's an excellent point. I recently pulled the macro algae out of the sump and turned off the lights. It was a lot of these clumps of bubble algae and they were clogging my return pumps down there. Recently I've noticed a bigger drop in pH during the night hours. This explains it. Have to get more useful macro.

 

[Randy Holmes-Farley Verified Community Expert]

The fact that there is usually a pH swing day to night shows that gas exchange is harder then most people think. Many claim their tanks are well aerated, but CO2 is often changing by a factor of 2 (for a 0.3 pH unit swing) or more day to night.

 

[Sophie"s mom]

The fact that there is usually a pH swing day to night shows that gas exchange is harder then most people think. Many claim their tanks are well aerated, but CO2 is often changing by a factor of 2 (for a 0.3 pH unit swing) or more day to night.

Yes! This is exactly what my tank does. PH is 8 in the morning, and 8.2 to 8.3 in the evening.