Here's my hardness:
And the thread about it: http://forum.simplydiscus.com/showth...gh-pH-question
I use municipal water and the pH swings from 7 or 7.2 out of the tap up to 8 or 8.2 when aerated for 24 hours. So I age and pre-heat all my water.
I'm sure someone else will chime in, but I've raised my discus from Stendker from 2.5" up to 5-5.5" without any issues related to hardness or pH (so far as I know).