You can't lower pool pH without chemicals.

Not really. Aeration raises pH (by offgassing CO₂), and rain is too inconsistent to do the job you need. If your pool pH is high, the only reliable way to bring it down is adding an acid — muriatic acid or sodium bisulfate.

I get wanting to avoid chemicals, but pH control is chemistry, not witchcraft. High pH causes scaling, cloudy water, and renders chlorine useless. Running your pump longer or adding a fountain will actually make it worse by driving pH up further.

Your options: buy the acid, or accept that your pool won’t be balanced. Those are the choices.

Sorry, but there’s no hack here. Just muriatic acid and good ventilation.