Tap Water Analysis.. Ro.. Ca/mg Question.

[jguit]

So i'm trying to get a handle on what i'm actually feeding my plants to both have healthy plants and satisfy my inner nerd. So here's the question. My water analysis put my ALK at approx 120 ppm CaCo3 (Calcium Carbonate) and my Ca at approx 90 ppm. I'm using RO water cut with approx 20% tap to stabilize my pH.

My question is, would the combined ppm of CaCo3 and Ca (approx 40 ppm 20%tap/80%RO) be an indication of how much Calcium is available to my plants? I've begun supplementing my fertilizer with approx 1/4 tsp of Epsom salt per gallon(approx 30ppm Mg/40ppm S) since my fertilizer does not contain any Mg and my RO/Tap mix barely has any Mg as well (lower than 5ppm).

Should I supplement my fertilizer with a bit of Calcium Nitrate as well to get a 1:2 ratio of Mg/Ca?

I'm currently running Jack's 20-20-20 @ 1/4 tsp (every watering) per gallon in soil @ a little over 4 weeks from seed.

Thanks!

 

[jguit]

Perhaps I'm not understanding the Alkalinity CaCO3 measurement. I'm reading that it's just a general term to express alkalinity and doesnt necessarily equate to Calcium content. Would it be correct to pay more attention to the "90ppm of Ca" value?