Ph of water and Soil

Hi, First time grower here. I just put my seedlings into G&B seed starter soil (mix of perlite, peat moss, pumice and washed sand). I had heard its best to keep water at a Ph of between 5.6 and 6.4. When I test my home filtered water with a calibrated Vivosun Ph tester (dont know wheter I trust this monitor yet) its at 8.4 and 7.6 for the tap water. My simple Ph tester for the seed starter soil shows it in the high 7’s.

What can I do to lower the Ph of the water and seed starter soil and should I? Thanks bunches

I used the stuff in the photo. I’m sure others will be able to recommend more natural methods, if that is what you might prefer.

5.6 is really low for a soil grow. It’s best to be in the range of 6.2 to 6.7.


Thanks FP. Photo is helpful! The soil is testing in the high 7’s

Welcome ,When you buy your pH Down, I would go ahead and get both pH Up and Down. You will need both eventually. I use the same As pictured by @FlxerPower


For seedlings I use store bought distilled water. Like you, my tap water is high PH. The most cost effective and organic method I have found Is citric acid. I start with 1/8 teaspoon to about 3 1/2 gallons. Test after 15-20 minutes. Add another 1/8 tsp citric acid if needed. Repeat as necessary.


I do the same thing as @SmoknGranny
In a peat based starting mix with distilled or RO water i dont try to adjust anything.
In fact I dont even check it anymore.Most seed starting soils are mostly peat or a peat/coco mix.
They have a pretty neutral ph and cannabis does well without any adjustment.
From there I transplant into Happy Frog and continue with Distilled or RO water until about the third or fourth set of leaves appear. Then I start adding nutrients very slowly…like 4 or 5 drops to a quart of water. Once I get up to about 1/4 strength I will start watching the ph.
This is just what I have worked out personally. Your results may vary… :smiley:


This is really useful advice Spiney. Thanks. My RO water seems to be high Ph, It adds calcium and magnesium salts which may be responsible. Good for the body, but mabye not so good for plants. I will try some distilled water and start watching the Ph after transplant, which I also plan to use Happy Frog.

Do you have a ppm meter (ec meter) ?
My RO water is 006 to 012 ppm and wont really test for ph…

Yes I have one, It’s 15 ppm.

Just use it as is. But use it soon after dispensing as it can become acidic if you leave it exposed to air for long periods of time…Like a day or more.

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I’m even cheaper. I use white distilled vinegar for down.


I’ve used citric acid for up and baking soda for down. It works.

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Citric acid powder in canning section cheap $5 per bottle and I am still on my first one and have grown many plants.
I now use RO water and don’t have to adjust as it will take the PH of the soil and you don’t need to check/adjust it…similar to distilled water.
If using citric acid it takes very little like from my tap Ph of 8.0 I use about 1/4 of a 1/4 Tsp or less to lower PH to around 6.5

Hope this helps

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I believe you have that backwards…citric acid = Down
Baking soda = up


Ooooops my bad

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I have been cautioned about baking soda for up. It is 8.8ph, but supposedly should only be used in a pinch. I have been told by people that know more than me that it can build up in your soil and cause other nutrients to be locked out.

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FixerPower, Can I ask is that same as what they use in hot tubs?

Same as for hot tubs?

I have no idea.