the pH controller/monitor is really only necessary when you have VERY soft water (a low Kh
level), where the pH might drop too quickly and harm sensitive fish (like discus for example).
I'm assuming you're going with the Milwaukee CO2
regulator, so that you've got a solenoid valve to plug into the controller if you get it?
Even if your water is a little soft, you can plug the solenoid valve into a regular lamp timer, and just have it turn on an hour before lights turn on, and off when the lights turn off.
If your water is moderately hard, you an run CO2
24/7. You'll see maybe a .2 change in pH overnight at the most, and this won't bother fish at all. The only downside is you'll use a little more CO2
than necessary, but at $10-$15 a 5/10lb fill, that'll last you months and months...its worth it.
Because yes, a steady bubble rate should give you a steady CO2
level in the tank and a pretty stable pH. Only those with a dKh
under 4 should be concerned about pH issues.