I need a beginners crash course in PPM

[George]

0.34 ppm? You mean EC? I hate EC because there are three different conversion rates to ppm, depending on the brand of the pH measurer you’re using . You can see that in the chart kindly provided by LabRat.

If your water tap is too low on ppm, so less minerals, you will need to complement with some Calcium, that’s OK for you to do it, here you can find some useful info on how they interact …

Quick question about Mag Sulfate

@SeymourGreen in general, you don’t want to change the calcium/magnesium ratio of your feeds, especially not for long periods of time. You are correct that if you add too much mag, it will antagonize your calcium and cause a deficiency. It is the same with potassium, too much K will cause Ca/Mg deficiency. Usually I would recommend supplementing Ca and Mg together, but also make sure you don’t add too much, or you might cause K deficiency (especially at the end of flower). K/Ca/Mg is a ratio tha…