i used to use RO water, but now pretty much just from the tap.
my water is pH 8.0-8.2 from the tap....
i try to hit 6.0-6.5, but even that is tough.
after mixing nutes/additives, i still
use a good bit of pH down.
i am pretty smale-scale compared to you guys...just a few plants.
after trying soil, DWC, waterfarm, and a couple more methods, this is the one i do best with. for that reason alone, i am sticking with the pro~mix.
here's another question for you guys:
do you re-use your pro~mix?
do you do anything to it to eliminate any "hot spots"?
i re-use mine. after a grow, i dump all the used medium into a wheel barrow, mix it all nice...add some worm castings and some fresh pro~mix...mix it all up again, and store in rubbermaisd containers until i need it again.