I just bought a pound of Macro Mix from Aquarium Fertilizers.com. It is made of equal parts MgSO4, KNO3, K2SO4, and KH2PO4. I used Chucks Calculator to try to get an Idea of what to dose, and, if I use a teaspoon per 10 gallons, I get 3.5 ppm Magnesium, 23 ppm Nitrate, 17 ppm Potassium, and 25 ppm Phosphate, respectively. Am I doing my math right? Isn't that a holy cow amount of phosphate in comparison?