Acceptable pH swings?

[Baldy]

So i just got my reefkeeper lite set up and the pH probe calibrated last night, and i noticed that i am getting a pH swing from day to night. before the lights went off i was at 8.0, and i notice this morning that im at 7.8. I have a bunch of chaeto in my sump on an opposite light cycle already. this seems a little large, or am i overreacting? if it is too much, what can i do to reduce the swing?