Thanks for the tip with the vinegar. I really liked my salifert calcium test kit but being under the influence caused me to put tank water into the test solution and not the test tube! lol hopefully the last time I do that.Good luck, IMO, I like the hanna for dkh and salifert brands bc they're accurate, fast, and easy. I really like the red sea calcium kit bc it seems to have the best color change but it does leave a calcium residue after each use just like their Magnesium kits. You have to use vinegar to clean them before using it again, which can become a chore. Dosing can take awhile to dial in but once you get it, everything will pretty much be on cruise control. More time to enjoy the tank, less time messing with it.