I'm cetainly no chemist but this entire thread appears to be a lesson in chemistry which in my view,, takes all the enjoyment from the hobby.
There are those who feel that domestic water softners as Byron indicated, replace one kind of mineral, the kind that builds up or furs inside pipes,, with another kind that doesn't. This water is said to contain too much sodium and not enough calcium salts and is unsuitable for fishes longterm health.
I might were it me,(and it ain't) go outside the house or apartment building and run some water from spigot minus any softner or R/O treatment. After letting this water set for twelve to twenty four hours ,,I would take ph reading. pH will rise after being allowed to offgass and what ever this ph value was, would be the water I used. If still measuring 8.0 to8.4 I would keep Livebearers,or cichlids or some rainbow fish. Problem solved.
I gave up my battle with my perfect 7.0 and leave it where it is. I run from an 8.0-8.6 regualary, it got too expensive to keep it at a 7.0 and well to be honest none of my fish seem to mind the Ph level being high like that, infact a few of them have grown drastically in this water as opposed to when it was kept at 7.0
I use tap water, de-gas it, de-chlorinate it and let it sit for 1-3 days before I put it in the tank, no less then 24 solid hours though( we got some weird stuff in the water here, right off the fox river)