PH concerns in flowering

What strain:   Blissful Wizard

Method:Soil Coast of Maine stonington blend. Supersoil designed for cannabis. Target PH of 6.3 

Vessels: 5 gallon Fabric

PH of Water,  Water in is 6.3-6.5 and runoff is 7.6

PPM/TDS :200-300

Indoor or Outdoor: mixed

Light system Sun when outside and 2x HLG 260 xl's in 44 tent 

Temps; Day 75-85 Night 60-70 

Humidity; Day, Night Variable with weather 50 - 85 RH

Ventilation system; Yes 6 inch 

AC, Humidifier, De-humidifier, No

Co2;  No

I will keep this as simple as possible.
plant has been in flower for 3-4 weeks. I have fed it twice since flower, both times with 1/2 recommended dose of Advanced Nutrients as per schedule. the second feeding was 3 days ago.
Today is a water only day. I decided to do runoff tests.
After one gallon of 6.3 ph @ 200 ppm runoff: PH 7.7 @ 1400 ppm
So I decided to run 5 gallons off PH 6.4 water through in an effort to lower PH.
After 5 gallons (1 gal every 5 minutes or so) PH 7.6 @200 ppm
So, no change in PH.
Another 3 gallons, still no change in runoff… gah!!
Frustrated, I did a slurry test 1:1 soil and 6.3 PH water. results: PH 7.0 @ 200ppm
So there is nothing left in soil for nutrients, and the PH is high.
This soil is designed for cannabis, and has proven great results. It does have a target PH of 6.3. I did my due diligence. The plant itself is budding nicely and hasn’t alarmed me visually.
I’m trying to stay ahead of potential problems as I near the finish line.
As an aside: I did top dress lightly with DE 2 weeks ago for gnats. I have read DE is alkaline. I can’t see that as making such a big difference?
Please advise me, I’m going to leave her be until I hear back from some of you old pros. She’s outside for the day. The light was nice as I was “flushing” so I grabbed the Macro lens for a quick photoshoot, lol

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Every plant is different, and responds differently. If the plant visually looks okay, go with your gut. I wouldn’t say neglect it, but you’re keeping track of the progress. I think you’re doing okay, as long as overall plant health is good.

The one picture you posted looked great.


@Covertgrower That’s where my head is at. I don’t want to keep running water through it if it’s not going to drop the PH. 10 gallons later it hasn’t budged. I will just monitor this every water/feed day. Should I feed her now being that there’s nothing left in the soil?

Yes definitely feed, especially a PK boost right now if you have something that will work.


I’ll just give her a half dose according to the Advanced Nutrients schedule @ week 3 flower and call it a day on this lady.
I have some seeds that soaked overnight that need to go into their solo cups and under a light!! I will start a journal for them. it will be my first official grow (seed to finish). I’ve learned so much from all the good people here! this place is fantastic (and no trolls!!)


We chase the trolls away, they get ugly quickly.
Tag me when you start a journal, I would be happy to follow along. Good luck on the seeds! Happy growing!


You dont use water to raise or lower the ph of your soil. Bloodmeal and dolomite lime raise and lower your actual medium. That’s what you use…


Awesome, I definitely will.

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thanks man, I will do some homework on that

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@Covertgrower I just fed her. PH 5.5 @1400 ppm going in. PH7.6 @300 ppm out.

I would drop the ph, and feed more often. She’s definitely hungry with that number coming out.

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Copy that. thanks again my friend

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For slurry test you need to use a neutral water source like reverse osmosis or distilled water.


Shit, I forgot about that. I will grab some Distilled water. My RO buddie is on the way.

When you say bloodmeal or dolomite lime to raise / lower ph, how does that work. My girls are 3 wks in flower. ph in 6.5…out 5.6. even tried going as high as 6.9 in still coming out at below 6.0. Plants look good. My question is which do I use and how do I use it? I hope I am not hi jacking your post bazoo. If so, my apologies. Thanks in advance shaggy

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No problem. Honestly I believe you just sprinkle some on top of your soil and when you water it’ll start changing it in your soil. But I may be wrong.
I have to really look into it more and learn completely how to start doing this myself. But @Covertgrower @Hellraiser I’m sure can explain.

This, if your plants aren’t showing any ph issues why change something that’s not an issue for the plant?

I have no experience changing ph with blood meal, lime will work, but doesn’t work very fast.
I use phosphoric acid, and change it that way. I have the concentrate version. A few drops will go a long way.

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no worries man, seems we have the same problem just opposite ends of the PH spectrum

I’ve never used any soil additives to adjust ph, never needed to.

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So does anyone know a link or source to read up on PH. Not understanding things annoys the F outta me. I want to know why water values going in and coming out are different, and what it means. I assume a runoff PH measurement is not the actual PH value of the soil. What is more important? The actual soil PH tested with a reliable probe? the water going in? The water coming out? A slurry test? I understand why we PH water (at least I think I do) to make the nutrients available to the plants when we feed. So if I’m feeding at 6.5 and the runoff is 7.6 what are the plants actually getting? Are some of the nutes locked out? This subject is way too frustrating and I need to be properly learned so I actually know what I’m doing in regards to PH instead of throwing darts. There’s plenty of information out there but I haven’t seen these questions actually answered in a format that makes sense.

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