Well, you can make sure the controller is calibrated by testing it against a liquid pH test kit first.
I've never had a controller, but realistically, it should run for a while, then shut off for a longer period than it was on, unless you have a ton of surface agitation quickly outgassing the CO2
and allowing the pH to rise more rapidly.
pH of 8.3 though...what is your dKh
again? with a pH of 8.3 normally, I would expect a rather high dKh
, something like 13-15dKh. If that were the case, dropping to a pH of 7.1 would mean you have more CO2
I just wanna make sure you've got all your ducks in a row