And it doesn’t concern you that a machine you paid $600 for is giving you readings for Alk that are almost a full dkh off? I purchased the machine expecting both accuracy and precision and it just won’t give me both for Alk. Ca/Mg are close enough for me, but when I have hanna/salifert/ATI ICP (with fauna marin confirming my manual tests are reading accuratly) telling me my tank is about 8.5dkh, and the trident is telling me my tank is 7.6dkh which one do you think I am going to trust? There should be no “mental calibration” where I add .85 or .6 depending on how far off their calibration solution is. That’s why I’ve tried to calibrate with my own water, but it won’t keep those numbers and automatically reverts to reading 1.5dkh below manual tests. There are plenty of people on these boards that say their trident matches very close to their manual tests AND that they can calibrate with tank water. Neither of these claims is true for me. I doubt anyone is saying that 1dkh is “close enough”. Further, Neptune even claims that calibrating to tank water is an option in their FAQ section and one of the things that made me more comfortable purchasing one after reading so many posts about how the machine is junk and their solution is ALWAYS wrong.