My preference is not to use the calibration solution provided in the Trident reagent kits. The levels are generally too far off (lower) from what I like to run my tank. I prefer to use my Salifert tests on Alk, Calcium and Magnesium and calibrate using those results. I also clean the mixing chamber of the Trident with a q-tip every 2 months when changing out the reagents. Super simple to do once you get the hang of it, don't even have to disconnect any tubes, just unscrew the 4 bottom screws and pop the cover off. Any stain buildup on the sides of the mixing chamber will slowly offset the results of the tests.