A lot of people who are pretty qualified do it the method you outlined, filling the calmag, then filling the nutes to the "target" PPM, but it's pretty misunderstood and is definately not a universal method accross all nutrient lines.

1st, pour your self a gallon or two of your RO water and add CalMag until you reach 250-300. Then you know how much mLs it took and just use that amount each time, no need to play with the meter.
2nd. Use your nutrient manufacturer's recipe for the growth stage. Whatever amount they call for, use that.
herbie the love bud Reviewed by herbie the love bud on . question and answer session...please Hi folks. I am new to hydro (coco) and have a couple questions. I am using Calmag because i am using R/O water with an initial ppm of 10. I am adding the calmag to 250-300 ppms. Now when i add the rest of the nutes do i add the desired ppm not including the 250-300? As in if i want the plants at 800 ppms does this include the calmag ppm? Another, as far as ph'ing my water. I just read in a mag that is is important not to have hguge swings in ph when adding nutes as this will cause Rating: 5