I've read that the HANNA tester reagent can drift over time. I also just got a ReefKeeper KH tester (plus). Testing with consistent values is nice, but if I get a drift is it the tank or the reagent? What I would like to know is if (and I am sure there is) a way to make (or buy?) a standardized seawater solution of a known ALK level so I can test the accuracy or +/- values of the test reagents.