I switched from Kent to Fritz and what I've noticed is a huge difference in calcium levels. I haven't test newly mxed water side by side but after a few weeks my calcium dropped from mid/high 400's to below 300 when I tested it. Lesson learned for sure. Test. Test. Test. Especially when changing things up! Magnesium levels in Fritz seem to be higher than in Kent. I've used Red Sea coral pro in the past but switched becaus of the cost. Again, this is just my experience.