Sherman
Has Met Willis
From everything I've ever gathered, it's not possible to accurately measure the pH of RO. It's simply too unstable and can bounce all over the place. My only experience measuring it myself was extremely erratic readings in the same container. It would drop to well below 7.0, then I'd use the pH probe to swirl the water and the pH would spike to higher than 9.0, and eventually decrease again. Because of this, I've never bothered trying to pH match my FW dips. My guess is it has something to do with the chemical make-up of what's in the water, and aeration.
As drastic as that sounds, I'd love to hear correction if I'm mistaken.
As drastic as that sounds, I'd love to hear correction if I'm mistaken.