Originally Posted by Civicman86
Either way Im reading 8.4 an hour after lights are out, which is what i get during the day.
Not enough time to make a difference. You will notice the biggest swing in the morning before turning the lights on and as you already know at night just before turning the lights off. Lighted water has little effect on ph but lighting plants/algae opposite the main tank or 24/7 does have an effect because of their ability to process CO2