I am trying to get my head around correcting ph. Today I fed with 5.9 and all were reading higher at run off.like 6.7-7.3.
I experimented by giving one some wate ph’d to 5 and it only brought it down 0.1. Would it be advisable to give like 4.0-4.5 for example to bring it down to more like the 5.9 I intended. Or whatss the best way I guess??
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You’ll risk harming the plant trying to flush with 4.0 pHed water. It would be best to go higher and use more gallons for your flush.
Some cannabis soils will correct to ~6.5 after a good flush.
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Welcome ! How confident are you in Your pH meter an when was last time verified in clean bottle of 7 solution or calibrated. Just my thoughts good luck 
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Curious what your grow medium is?
Do you know its ph? Did you do a slurry test if soil? Did you amend the soil like adding dolomite lime?
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Fsorry yeah new pen in coco and perlite various strains 600 ups 20/27c
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Don’t measure runoff pH in coco. You’re illustrating exactly why you shouldn’t measure; knowing causes you to push your input up.
Measure your input pH, fluctuating between 5.8-6.2. Measure your input ppm. Measure your runoff ppm (should be higher than input). But don’t even measure runoff pH.
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The concept with coco is that every watering resets the medium. What happens between watering is that the water gets drawn into the plant through osmosis; nutrients enter the plant through transportation. The water and nutrient uptake are decoupled. At the input values we use, the water that remains in the medium becomes more concentrated (with nutrients) over time; this change in concentration as well as other processes inevitably change the pH. It’s nothing to be concerned about, because we can reset the medium by watering fresh solution which flushes out the older solution.
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This only refers to coco? This makes sense given what you say later about resetting. In soil, I tend to rely more on my ph runoff numbers than ppm. My ph will be consistent 6.5 - 6.6 +, but ppm will be 2000+ for a couple of weeks, jump to 4000, then back to 2000 while there is virtually no change in ph.
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Same for soil. Soils like big roots, ocean forest and some others that I can’t remember right now, like to sit around 5.8 in runoff (especially by the time the plant is flowering). This used to freak me out and I would try and fix, and that’s where the issues would start. Now I just let the soil buffers do what they do and ignore runoff ph.
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When growing in soil I use OMRI listed bagged soil, and heavily amend a large batch. The buffering capacity of my soil, which I try to get to 6.5 out of lab tests, is so high I don’t worry about pH from there. I use 7pH municipal water, a little soap, and I’ve been using Recharge. I’m thinking of switching from Recharge, but I have enough on hand for years.
I don’t measure my runoff at all in soil, and I try to keep it to a minimum.
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I would freak out too. I start thinking it is time to flush if it drops to 6.3.
Are you seeing signs of deficiency when your runoff drops below 6.3 pH?
I have but it wasn’t due to the runoff ph. It was caused by low magnesium inputs (I wasnt running cal mag or Epsom salts at that time) and ended up causing more problems trying to correct runoff ph. The last several grows I’ve done have been fine at 5.8 runoff with higher magnesium input.
No I do not and attribute that to heeding the early warning signs. How does that sound? In truth I may be a little too cautious because of a bad experience when I did not measure ph & ppms. My soil mix has a ph of around 6.7. So if I get a major drop off of that number I attribute the decrease to salts accumulating in the soil. If I hit the 6.3 - 6.2 on runoff, I immediately run and couple liters of ph h2o through. And them move on. I have not had to do a major flush since the one time.
Overly cautious?
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@KeystoneCops, great explanation, really glad I got in on that…have about 12 grows under belt and this is first time I’ve started looking at ph,i use coco and am so glad I read your post here…explained alot for me,ty,never had problems with any grows so I never felt need, lol.
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And I thought I was getting pretty knowledgeable about growing in Coco, and have been wondering why my PH tends to increase as the grow progressed , had no idea. learned something new today, thank you.
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Your reservoir pH will climb naturally due to bacteria unless you use a sterile solution with peroxide. So that could contribute to some of the pH movement you’re seeing.
I’m just echoing Dr. MJ Coco.