Guys, let me stress that consistency is more important than "perfect" numbers.
Lots of guys and gals are reefing at the top of our hobby with pH's at 7.8 cal below 400 etc...my calcium stays at about 400...but I cant get my alk up to save my life...tried everything except a reactor.
In the end I realized that my corals were growing well, and that they were less stressed when I wasnt tinkering with stuff. So I have left it alone. Its usually around 6 dkh.