I had a thought! (yes it happen)
Dissolve Co2 in our tank stay stable at a certain level beacause we supply a stable flow and we lose it in the air at a stable rate so what's in the tank stay stable to. but, with those ph drop checker, CO2 that gets inside can't get out so Co2 level in the kh ref solution should get higher and higher with time and one day, we'll have way more Co2 in the ph drop check that we have in our water. is this correct?