PPM for marijuana flowering stage


A question from a fellow grower:

this is indoor hydroponic, 400 watt tent ,6.2 ph white widow and blueberry. What should ppm be in flowering stage?


Depends on a few different things. What type of nutrients are you using? What type of hydro setup are you using? Deep Water Culture? Flood and drain? Are you using r/o with a 0.0 ppm starting point? Or tap water?


You will be safe at a PPM range of 1000-1200. This might be a lighter solution, but again it is going to be different with some strains. It is definitely a safe range :smiley:

Oh yeah. Maybe lower your PH to 5.8-6.0


If I added nutes, and ppm was at 1400 (week 4 feeding, fox farms recommended feeding schedule, full strength), and after an hour the ppm went down to 900… What should I do? Add more now? Wait a day and add more? Or is adding more a bad idea? Should I wait until the weekly water change is ready, and then just add more nutes to the new water? I’m at a lose as to what to do because I keep thinking I could do this or do that etc.


As long as my PH was stable; In would leave it alone. 1400 is a strong solution. My 1st thought was; You did not mix and wait long enough to get a proper reading. If you did then here is a lesson for you.

When you feed a plant and come back to see a drastic difference in PPM, you can follow this old school hydro farmer’s rule: If your PPM starts at 1400 (confirmed), and it goes down to 1`000 overnight; This indicates that the plant uptake of nutrients was stronger that the desire for water. Generally, this is considered a sign that the solution is too weak. Plant is removing minerals and not water.

ON the other hand: If you start at a PPM of 1400 (or whatever), and you PPM goes up overnight; It means that the plant is got all the nutrients it needs, and drank only water. A sign that the mix is too strong.

I would monitor the situation before making any drastic changes. If you are at 1000PPM; See what happens. See if the PPM continues to rise, or stay average.

Another thing; I add plain water PH’d correctly in between my reservoir changes in hydro systems. :slight_smile: