My Hagen test kit has also proved to be as accurate as the Salifert kit-as with Sam, I have also used both.
Like Jonathan mentioned-400 ppm is not too high, it's in pretty good range, maybe a little low but not that bad at all.
Calcium is a chemical that is hard to get a precise measurement with regular test kits-thus that's why we have to add so many drops before a chemical reaction takes place, just the same with alkalinity.
cheers, Rich
