You are correct. Any system that relies on the accuracy of a pH probe in your calcium reactor to turn on and off is ultimately at the mercy of the pH probe. The explanation I shared earlier is an attempt to offer my opinion on why I think a two-stage regulator is superior to a Carbondoser. I have used both. The two-stage regulator gives you a remarkably consistent flow rate independent of a pH probe. I use my Apex with a pH probe in the calcium reactor for an emergency shut-off only if things get out of control (never happened yet). I hope that helps clarify what I was trying to say.