Its either ADA has a special setup, or its basically wrong. By stoppnig CO2 as well as aerate the tank at night, CO2 level will drop dramatically hence pH will rise very rapidly. And if the tank is already saturated with oxygen before lights off, aerate the water will in fact drive off extra oxygen very quickly.
BTW, plants "breath" 24 hours a day (it doesn't stop during photoperiod), just the amount of O2 -> CO2 is by very far smaller than photosythensis' CO2 -> O2. But plants continue to consume just a tiny amount of oxygen even at night.
On the other hand, 90% of CO2 we lost is to atmosphere even during the day, NOT due to photosythensis, so at night, the amount of CO2 present, even if we keep the CO2 injection unchanged, would only be at most 15 - 20% difference, a 0.2 shift of pH max.
If one insist to turn off CO2 after lightout, and bringing up the air pump, and vice versa during the photoperiod, although I don't see the need of it in a healthy planted tank. I would suggest NOT to turn on the air pump for the first few hours of dark period, keep CO2 injected all the time, and shut down the air pump at least an hour before light on to allow CO2 to build up again.
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