Air intake nac9 for ph

[Silverni2]

I'm having trouble keeping my ph up at nite, it tips to7.7. I've been told to add plastic tubing to the intake on my skimmer which is a bm nac9 and vent it outside, exactly how shoud I do this?
Thx
mixed reef 120g with 30 gal fug and sump

 

[Chiefmcfuz]

Ph rises in the day and drops at night naturally. To make the changes in ph smaller run the lights on your fuge opposite the tank lights.

 

[Silverni2]

I so that cheif but my tank is in a basement and in a wall that also houses my heating and airconditioning system as well as my hot water heater. I believe this is making I significantly harder to raise the ph