Remineralization Cartridges: Thoughts?

[Aquattro]

I'll read it when I have time, and offer my interpretation. Apex is this weird little device everyone but you seems to have, it controls aquariums and has a pH probe.
But here's the basics. You stated, from your interpretation, that pH measures salts. It does not. It measures the molar concentration of H ions in a solution. Pure water has a theoretical balance of H and OH ions, giving a pH value of 7. Given the experiment above, you will find that your pH meter of choice will give you very very close to that value when you measure it. Within the error scale of the device you're using. I've used high end lab equipment to perform this test, and received an accurate measure of 7.0.
Now Randy is a smart guy, way smarter than me on my good days. So I'm sure there is some truth to whatever he's saying, and I will read it, honest, but I don't think he's saying what you think he's saying. If I get bored, I'll even go talk to him about it
You do further state "within hobbyist's capabilities", so slightly moving the goal posts, so I can't address both items. My initial statement that pH measures salts being wrong stills stands.

So here's the take-away. For hobbyist purposes, you almost never have to worry about pH. The salt mix takes care of putting it where it needs to be. If you have a pH meter and just want to test stuff, whether your tank, tap water, or glass of orange juice, your meter, being a cheaper hobbyist unit, will still give very accurate results for your purposes. SW is about 8. Tap water will be about 6.7 - 7.2. Orange juice is high 5's, as I recall.
In the end it doesn't matter, which is why I'm not terribly concerned with reading more stuff. But I will try to fit it in