How to control PH at night ?

[Casey8]

I am putting a very long hose to connected to my skimmer valve and go straight to my small air vent in my bedroom 24hrs. I am also planning to put a big blanket to cover up my small refugium so the light is left on the whole night to control the PH swing. I really don't like the way it has changed too much from 8.3 down to 7.5 in the early morning.
Thanks for your inputs, guys. I hope I can find the solution to deal with this problem.