PharmaZanswered grow question 6 years ago Hey there. I’ve written a reply 3 times now and it didn’t send. Basically to shorten it down. If your tap water is around 0.4EC before adding nutrients as long as the nutes you use and the soil is of good quality you may never need it. If you live in soft area like me (0.1EC) you need it. Only in small amounts in soil, but every feed with coco. —————————
Deficiency signs can show weeks after the requirment for either Ca or Mg. So this is why growers always supplement Calmag, unbeknown to most that when a deficiency shows up it was because the plat didn’t have enough/access to calcium or magnesium. So the moral of the story is always use it but find out how much you need. You need at least 160ppm of calcium every feed in veg and flowering stretch, 2% of that total calcium should be added as magnesium so 30-40ppm of mag is enough. Hope that clears things up✌️🏻