I do my water changes with remineralized RO. I raise kH with sodium bicarb and gH with Ca and Mg. I'm confused as to how much of each to add, and how ppm is calculated. For instance, I just added a 2:1 ratio of Ca:Mg to 10 gallons of WC water. The Ca bag says 1/2 tsp is 10ppm and the Mg bag says 3/4 tsp is 10ppm. After adding 1/2 tsp of Ca and 3/8 tsp of Mg, the gH of my WC water increased 1 degree/17.9 ppm. 10 gallons equals 38 liters, so shouldn't it have taken 38 times that amount of salts to raise 10 gallons of water 1 degree?