You do not need to adjust the pH until the tank is fully cycled and you start adding live stock.
Test the pH at the same time each day when testing. You'll get your lower value just prior to the lights going on and the highest value in the evening before the lights go out.
Test the pH at the same time each day when testing. You'll get your lower value just prior to the lights going on and the highest value in the evening before the lights go out.