[piercho]

Sarah,
2-Part Solution, an RC sponsor, sells the dry chemicals to make Randy's Ca/Carbonate/Mg additives. They have the chemicals either in bulk or in pre-portioned packages to make standard solutions of known concentration. There is also a calculator on their website that will assist to figure out the dosing volumes of the standard solutions. If I knew another site offering the dry chemicals in conveniant volumes I would point it out, but the only one I'm aware of is 2-Part and I have used them.

JetCat, I'm saying that I think that the 3:5 ratio winds up being balanced (with respect to Cl and SO4) only if you have Na and Cl being added from the other parts of the two-part solution. To get the final ion ratios in table 2, I think you have to use all three parts. If you are using limewater and/or a calcium reactor instead for Ca and carbonate you aren't adding the Na and Cl that would be added if you were using 2-part. So when you use part 3A for Mg, your chloride and sulfate ratios increase with respect to the other major ions. And the sulfate ratio could climb quite steeply. For people not using the Ca or carbonate 2-part components, I would think that you would want to use mostly MgCl to boost Mg, as Randy said in the origonal Mg supplement article.

That is how I figure it, but I'm no chemist that is sure. And it seems if you exchange enough water frequently enough, the major ions should stay pretty much in line anyway. At least thats what I took away from the Randy's Mg supplementation article.