Just beware cheap CO2 meters can drift over weeks and months and need to be calibrated a lot. We use expensive ones are work for IAQs and they require annual factory calibrations a daily bump checks with span gas with known concentration. The way to somewhat combat that is monitor the difference in concentration outside and inside. Ideally, if your indoor concentration is no more than 700 ppm more than outdoor concentration, your make up air is adequate for your occupancy. The +700 ppm is for personal comfort and not tank pH but it might be a good reference point.I scored a C02 meter from amazon and was surprised just how high it was in my home. Two people a small dog and a cat can create a lot of C02. The BSR C02 scrubbers work. I found that running one brought my daily average up from 7.6 ish to 7.9. You do have to make sure you keep a little water in the bottom of the reactor and change the media when it turns blue. I then added a kalk reactor that tops off about an hour before the tank ph low (around 6 am) and this brought it up to a daily average of 8.1 or so.
I know my pH is always lower in weekends when my wife and I are home all day.