Ph dropping, help

[cane]

My newest tank has been set up since nov 2017. It’s a 240gal tank with basement sump. 350 gal system. I run an apex controller. My PH has dropped from an average rang of 8.1-8.2 to 7.98. I dose alk. It’s mainted the same PH since I started this system. Please help, what’s going on. What do I do

 

[Larry L]

Have you calibrated your probes recently?

 

[Randy Holmes-Farley Verified Community Expert]

The pH is fine, but if it really dropped as opposed to test error, then the explanation (assuming normal alk) is higher CO2 somehow, probably from your room air.

This as more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/