I got mine kind of balanced to where it does not hit extremes, the airstone runs lightly all day (inside a breeding net) and I never switch off the CO2.
In your system, the airstone will cycle CO2 rich water to the surface where it will try to find equilibrium with the atmosphere (off gas), so the CO2 would be reduced and oxygen would be increased (when it is low).
Manual, is the snake's name, and he will bite you sooner or later.
Cape Town, South Africa.
Hi. I'm back.