Should I add CalMag?

Maybe not EVERYTIME. But every 2nd time sure.. as it might be low in that water. Or you could wait to see a problem then correct it.

 

Magnesium will be a problem 4 weeks before it shows. I would add every other feeding. If your ppm is 0 you have absolutely nothing in the water.

 

Every second time is good

or like me foilar spray 1-2 times a week

just for something to do ....lol

good luck

 

If your ppm is truly zero, then I would definitely recommend adding some cal mag. Calcium is very important when growing strong and healthy plants!

 

epsom salts if you see a mag issue i uss it most waterings

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I have 0 ppm water as well I add 5ml/g till the end of week 5 in flower. Works like a charm.

 

After week 5 no more calmag, why?

 

I added it every 2nd feed in DWC

 

By that point you don’t need to be adding any sort of n to your plants. There’s nitrogen in my calmag so I cut it out. Plus by then the plant should have enough cal and mag stored up to cover till the end. A setiva that runs 12 weeks I’d probably carry it out to week 7.
I cut out everything about 10-14 days after that except for microbes and sugars.