Ph not coming down!

I am having trouble getting the soil ph down…it is staying around 7.5 to 8. I have been adding and adjusting the ph down to 3 now and still no progress and the soil will not change…the plant is showing a bunch of stress and the leaves are taking it hard. Any suggestions on how to get this in the right direction and save this plant ? It was started in early October and I want to get her healthy before I switch to flower. It had went from having 11 inch 13 fans to a miniaturized version now that is struggling but a pretty tough plant ! Plant is and has been for a long time 16.5 inches with four tops and six side branches with numerous growth tips forming up the branches. Would love to get it to branch out a bit more and get it to flower already as it is time ! Two clones have also been taken off with the hopes of them surviving yet to be seen

Strain; Would be a bag seed…indica/hybrid
Age from Sprout: October 7 was sprouted

Soil in pots, Hydroponic, or Coco / Brand and type of Soil & Size of Pots: Potted in a 5 gallon air pot with a mixture of black sand/pro mix bx mycorrhizae/perlite. Was started off in a solo cup and transplanted into a 2.5 gallon pot…then to a 5.

How often do you water and how do you determine when to do so? Watered every week and let dry out till the top is dry down two inches. Problem is the plant is not using the moisture quick enough and the dirt is not the problem as it is porous enough and has a lot of perlite. Soil probe is used as well as a soil test kit.

PH of water and runoff or solution in reservoir: Using RO the entire time anywhere from 6.6 to 6.8. Started adjusting the level down with lemon juice and vinegar when the soil probe had shown alkalinity rising. First timer so thinking I can just keep adding ph down to fix the problem and no I have not flushed the pot. Started out being an unbelievable plant and is slowly withering. Was adding a 50 % felt mix of 15-5-5 and thought it would be enough to keep the ph in check.

What is strength of nutrient mix? EC, or TDS: NA

Indoor or Outdoor: Indoor
Light system, size and height from plants: 6 x 9 watt full spectrum led veg lights on the tops…2 being flowering model with magenta and two 26 watt cfl full spectrum bulbs on the sides lighting lower branches

Temps; Day, Night: 78.8 day/ 71 night
Humidity; Day, Night: 50 day/ 65 night
Ventilation system; Yes, No, Size: No
AC, Humidifier, De-humidifier: ac/humidifier/dehumidifier/fan all on the go
Co2; Yes, No: yes

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Strain; Type, Bag seed, ILGM… name of strain:

Age from Sprout:

Soil in pots, Hydroponic, or Coco / Brand and type of Soil & Size of Pots:

How often do you water and how do you determine when to do so?

PH of water and runoff or solution in reservoir:

What is strength of nutrient mix? EC, or TDS:

Indoor or Outdoor:

Light system, size and height from plants:

Temps; Day, Night:

Humidity; Day, Night:

Ventilation system; Yes, No, Size:

AC, Humidifier, De-humidifier:

Co2; Yes, No:

Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the point questions and facts will help us help you.


If you would fill out that form for starters, I can almost guarantee you we as a group here will help you turn her around. A picture would really help as well

Welcome to ILGM.

Im sure others will be along shortly.

How much water at ph 3?!?! There is definitely something not right here. Have you flushed this plant?

You can try a solution of 50/50 cold coffee & h20.

Gave it a liter of ro with half rate of Epsom…kelp man and 15-5-5 with micros then took the ph down to 3 to try correct the soil ph

pH 3 is VERY acidic. Each integer of pH is 10 times more acidic that the previous higher integer. I think you have probably killed your plant.

For a 5 gallon pot, you need a lot more than one liter at a time. You probably built up the nutrient salts in your pot to levels too high to sustain healthy growth. You should have flushed it with about 20 gallons of pH 6.5 water to wash out the accumulated salts and then tried adding some pH 6.5 nutrient solution.

On your next grow, you might want to add some peat moss. That is pretty acidic. Or maybe try pure coco coir: It is pretty inert so the only thing affecting pH is the pH of the nutrient solution you just dumped in. Every time you dump more in you use enough to have 30% drain out the bottom. That washes the accumulated salts out.


I totally agree with @1BigFella , 3ph will flat out kill ya girl.
And also about the flushing procedure, at least 3x’s the size of the pot.
But you never go under 6.2 or over 6.9 when trying to correct ph.
If you do it will stress ya plant and exacerbate the problem


If it was me, depending on if I thought she had a chance to survive or not (wish you would post a photo of her). I would immediately transplant her into fresh Promix without the blacksand, and water her at a PH of 5.8. You’ve been watering at way to high of a PH for Promix. You also need to get a proper digital PH meter. Those soil probes are worthless.


I water 6.3-6.8 in promix @Rugar89
No issues
I di agree with the soil probe meters are junk
I think the issue here is how they are correcting the ph
Using ph up or down is best imo
Otherwise the folks have you covered @Steve-o

I agree with @Countryboyjvd1971. You were probably just a little off until you started hitting it with all the other stuff. It hangs in mix too much.

I’d run that 15 gallon flush ph’d somewhere around 6.0 adjusted with proper solutions. And test the last little bit of runoff. If you made up ground, just continue watering to runoff when you water.

I wouldn’t even necessarily bother feeding with your ph all jacked up. The plants won’t see any of it. Maybe a touch of something to get the ro to react to the ph adjustment solution.

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Thank you for your help…but I have one problem and that is the soil is not full of nutrients as the soil test I have done shows that there is no residual fert in the soil.

@Steve-o can you post a picture of the the problem plant ?

Could putting egg shell powder have anything to do with this ? I had put a bit in the root zone when I had transplanted into the 2.5 gallon. Thinking it would have given a calcium boost

I still stand by it was your ph adjustment techniques
That caused your issues
I use promix myself water at 6.5 regularly using ro water only difference is i use ph up and down
You mentioned that your soil test showed no nutrients in soil
I suggest you get a peoper ph meter and get ph in check the probes dont work and you probably over adjusted to get the readings to move on dual probe meter

The egg shouldn’t have caused this issue

I did just get a ph pen and will be going by that more now…it’s just hard not to use the probe and see what it says…so as of right now I’m getting ready for a 15 to 20 gallon flush at around 5.8 to 6. Let it dry out and she gets a proper feeding depending on what the run off says at the end. I didn’t want to do this but looks like I have no choice. And if something goes wrong I guess I can start over…or maybe a guy should have just ripped it out anyways and save some time…all a learning curve and it’s the only issue I’ve had but it’s a real problem !

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A flush is a goid idea I wouldn’t flush lower than 6.3 myself @Steve-o and never trust that probe style meter the are notorious fir being inaccurate
Moisture reading is ok tho

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My bad. I thought Promix was PHed as a soilless medium.

I agree, that egg shell probably not your problem. But it does note a potential issue. Generally speaking, to use things like egg shells in your favor, you need to create a compost. It’s a whole entirely different method which requires time for the soil you’re creating to work. You wouldn’t just throw things in the pot with your plant as you went.