Ridiculously hard water as CalMag supplement?

  • Thread starter matsc
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So, got bored and was doing some math earlier and I came to realize something. GH's CaliMagic supplement is by volume, 5% calcium, 1.5% magnesium, and at their recommended dosage of 1mL per liter, you end up with a solution of 50ppm-Ca and 15ppm-Mg.

My tap water is ludicrously hard, over 600ppm TDS, and in the neighborhood of 250ppm Calcium (unfortunately my town doesn't specify how much magnesium is in there, but other cities in my state suggest it would be about a quarter to a half of the calcium value, so somewhere in the 60-120 range would fit)

My question is... could I use this tap sludge water on its own as water, dilute it with RO, or go straight RO for my plants (and use the tap as a calmag source if deficiencies appear). It has a fairly high chlorine residual (~2ppm at the well), but a pinch of vitamin C powder takes care of that in short order, so no worries there.

In the past I've used RO almost exclusively out of a sense of paranoia, and supplemented with CalMag when needed, but since I have actual numerical values to play with now, I'm curious of folks opinions. (And, well, RO is expensive, and my kitchen tap doesn't require me to walk a half mile each way in 110F+ temperatures)

Additional fun fact: I also now know how much uranium is in my tap water. Yummy.


Shouldn't be a problem. I have fairly hard water as well (Starting EC approx 1 EC w/ 150ppm Ca) and mix it with RO. I use a fertilizer that has a decent amount of Calcium in it already. If i ever spot a Calcium deficiency, I just slightly up my feeding EC and never have to use suppliments. My reason for mixing tap and RO is to add a bit of alkalinity back into the water to keep the pH of my growing medium from crashing but the extra Calcium is a benefit as well since i grow with LEDs.
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