Calibrated my pH probe this morning with 2 point calibration. 7.01 buffer and 10.01 buffer. It’s the red Hannah pH tester, it’s the one that has the little glass sensor at the bottom.
I’ve also had tests done before at LFS pH is still in that range.
I’m in a few other groups and they recommend Kalkwasser, I just have to learn how to dose it before diving in.
My scrubber media has yet to change color,.....
I have never used one of those ph testers.
Do you have a dosing pump? or do you manually dose AFR?
If you already have a doser switching to a hydroxide based 2-part will be easy.
Kalk (calcium hydroxide) provides about the same ph boost as Sodium Hydroxide but you consistently add it to your top off or use a reactor. Kalk Slurry is an option but I found it to be a lot of setup and work to maintain. IMO Sodium Hydroxide based 2-part is easiest.
In short Kalk works but I find it more of a hassle than 2-part.
A lot of scrubber media marketed for reefing doesn't change color very well, I use this stuff, the color change is very clear, and it is cheaper to buy it in 5 gallon jugs.
If everything is working correctly I doubt your CO2 media actually lasts 2 weeks with a 7.6ph.
A tank that I just restarted sits around 7.9 and burned through 2 liters of media in 4-5 days.
https://www.shopmedvet.com/Soda-Lime-3lb-Bag-J0553
For PH there are 2 main influencing factors you can control
Amount of air exchange (with low CO2 air)
The Supplement you use
There are other little things like cleaning up any detritus in your sump but at the end of the day those 2 things make the biggest impact.