For example, opening the windows to the house makes my ph jump to 8.3, but drawing fresh air through my skimmer has minimal impact. It’s interesting to think about though.
I noted earlier in this thread, and elsewhere previously, that running a fresh air line has historically made no difference to the PH in my tank. I do run a fresh air line, though mainly to muffle the sound of the dual mazzei venturi. It makes intuitive sense to me that in my system, at least, fresh air to the skimmer would make no difference. It simply not enough to offset all the open top bodies of water in my system that are absorbing CO2 from inside my house. Now, if I run a blower to exchange the room air that does make a difference. But that is only practical during the temperate months of the year. Otherwise I just don't OCD over it.