I have any air pump with air stone already in my sump when I tested mine.I might try that too, yeah, but it seems a good idea to do the test in the house first, just to see if the extra aeration from the airstone is what’s raising the Ph, or is it really just the air used -outside vs. inside -scientific method and all
If it's CO2, your air pump will be pulling the CO2 from inside the house.