They are not the same mix, our salt is basically to HW Marinemix, what Reef Crystals is to Instant Ocean. It has a higher calcium level and higher KH and Magnesium. I also always used HW, it is generally considered one of the best salts you can buy. HW has a calcium level of around 380 and a KH around 8 and Magnesium around 1300, it is essentially identical to the parameters of NSW. Our salt should give a result of 410, 9 and 1350. A few other minor elements also have slightly higher levels. I would not dissuade you from continuing with Marinemix, for what its worth they now offer there own reef blend, the HW importer is a close friend and if you need help locating it I can get you in contact with him, I don't like to compete with him even though we carry competing lines on some items.