Ph issues and can't find a solution

I have problem with my ph in my medium. I can’t drop my ph and it’s staying at 7.8 even if I run plain h2o ph at 6.3 I need help.

Strain; Type, Bag seed, ILGM… name of strain:
Maui wuai
How many plants: 4

Age from Sprout and Flower: 63day and 3wks

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

How often do you water and how do you determine when to do so? Every 4 to 5 days pots fell lite

PH of water and runoff or solution in reservoir: 6.3

What is strength of nutrient mix? EC, or TDS: 600

Indoor or Outdoor: indoors

Light system, size and height from plants: 300w led at 24in and a 125 cfl at 10in

Temps; Day, Night: 78 and 70

Humidity; Day, Night: 50 and 60

Ventilation system; Yes, No, Size: yeah 6in

AC, Humidifier, De-humidifier: no

Co2; Yes, No: yes

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Good evening.:slightly_smiling_face:

Do you have some PH down solution?

If so you should be able to correct the issue.

I see you’ve been here a few weeks but welcome to the forum anyway @BigPappa420

Are you using one of those prong meters stuck into the soil? If so they are notoriously inaccurate.

The best way to measure the ph of your soil is either a slurry test or measuring the water that runs off at the end of watering.

BUT All of this depends on several issues. Let’s get the full picture!

Please do the Support Ticket So we can give you an accurate answer!

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

How many plants:

Age from Sprout and Flower:

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

I do and I flushed with 5.8 ph water

Try not to flush with extra low PH because the end result will be your soil falling to that PH.

If you are trying to correct a high PH soil issue with lower PH water then just water it with that water, don’t flush it with that water.

If your checking your run off then you should slowly start to see your run offs PH decline with each watering. Once your run off has achieved the desired PH then begin watering with your desired PH (6.3-6.8)

If you want to flush then flush with water between 6.3-6.8 assuming your in soil.

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Many commercially mixed soils like Fox Farms , etc have a ph set at 7.0 as they come out of the bag.

For the first few waterings and / or feedings your runoff slurry will be high if you adjust your water and nutrients to a normal level.

Taking into consideration the soils buffering at 7.0 and the fact that you are adjusting accordingly prior to watering you simply adjust the water with nutrients or not down into the low 5 PH range.

When you water you should receive the lower PH reading that your wanting to see from your medium because your now adjusting your PH according to the mediums set buffer.

That PH buffering will lower after each subsequent watering.

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I run 3gal pots and promix hp soilless medium. I’ve tryed wat you guys have told me and with just 25% runoff it still reads 7.8 I used i have calibrated my meter

Pro mix I’ve read holds onto a lot of salts from synthetic based nutrients.

Because of this it will keep PH stubbornly high.

Flushing several times with water as close to 0 ppm and with adjusted PH should bring it down but it takes several flushes to do so.

What if any nutrients are you using?

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I used to run age old. but I’m using dry amendments on this run. I started having problems when I switched to flower there 3wks in. There where showing signs of nutrient burn and my lower leafs were really getting ugly the tops of nice in color except the lower parts.

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I just started having high ph issues with promix. Usually I was too low but lately 2 have crept up to 6.1

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In my opinion flushing several times with 0 ppm water is necessary at this point.

The soilless mix both of you are using has a high concentration of salts thus the PH issues.


Yeah its was pretty high. I flushed a wk. Runoff tds was 650 and ph 7.8. I watered yesterday and my ph is still 7.8 with a tds of 670

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@Alton66 hey bud, just a note here, he could use some of foxfarms sledgehammer to clean out those salts and unneeded nutes. That is what I am using on my main grow. Or he could use another brand that does the same or similar.

You can either just water with the sledgehammer or do a flush. Your option. I havent done a flush yet, but used it when I watered and it worked like a charm.

Forgot to add that it will lower the ph.


First off promix HP is soil less needs a ph of around 5.8 so if you can’t get ph to drop lower your ph even further 5.3 or so let the ph drop slowly over a few regular feed and water cycles



Yes he sure could. Any flushing agent like Sledgehammer would help in the flushing process. :+1:

@Alton66 Very true, but with Sledgehammer you dont have to do a full flush till near the end of your grow. Monthly its used to control salts and buildup of excess nutes using it in a regular watering of your plants. Used it once so far with my main grow and I even saw the salt stain on the side of one of the pots go away for the most part. took a few days and another watering of plain water, but wsnt expecting that.

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@Countryboyjvd1971 you use promix bx. Any thoughts? I know this is considered superior to coco but I haven’t used it.

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I’m actually loving it so far @Myfriendis410
I don’t see myself going back to the ff products anytime soon
I have never tried the coco
I like the fact there no nutes in the medium and roots seems to grow faster and healthier in it over soil
I’ve been watering at 6.3-6.5 as nectar recommends as well with no issues


@Countryboyjvd1971 have you got any thoughts on @BigPappa420 issue with promix?

Personally I would flush at the low end of nominal (5.5) and feed at the lower end while monitoring the ph out.

Remember that nutrient deficiency and excess will look similar in soilless @BigPappa420. Your tds values were not high.


Let take a look @Myfriendis410 I must have missed something here lol

I would be interested it type of meter being used @Donaldj has mentioned the soilless thing above and phing at 5.8
Something doesn’t sound right for sure
@BigPappa420 when your having a issue with you medium in this case promix and you can’t get it to adjust you’ll need to do as @Donaldj suggested and water either higher or lower
If 6.3 isn’t doing it lower to 6 and try again
Also you can have. A nuts build up but with ppm is the 600 I don’t think so these almost no nutes in medium so I don’t think flushing is necessary
I use organic nutrients and they recommend a ph of 6.2 -6.6 depending where in the grow and I’ve been following that with out issue
Try a lower ph water next watering
Can you post a current picture as well