This theory is more for fish then plants even though you are not injecting into the water I assume. Yes CO² injected into the water will keep the Ph in check just like for fish tanks.

If you are growing in Hydro then you need to balance the Ph twice a day minimum. Save the CO² for the plants when the lights are on. CO² enhancement does the plant no good during the dark period. If you are using CO² you must also have HID type lights too. Fluorescents do not have enough light for the plant to process the extra CO² so you must have HID lights.

The Ph in a Hydroponic system will move up as the plant uses up some nutrients and deposits waist back into the reservoir. Just keep your Ph in balance and don't worry.

Nobody said Hydro was easy and required little work to succeed.

Dirt is easy and simple but Hydroponics requires attention and work.