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pH out of control


New Member
Hello everybody,

This is my first post here, so greetings to y'all : )

OK, the problem:

I use organic soil, the following mix:

53% Organic potting soil
25% Perlite
10% Vermiculite
12% Worm Castings

My nutes: BioBizz, I use BioGrow, BioBloom & Alg-A-Mic.
The strain is Jack Herrer. I use RO water for irrigation (TDS < 40).

I am using clones, root them in small plastic cups, repot into 1 litre pots for a couple weeks, then into bigger pots and into bloom. Been using 1.7 gallon pots for flowering for awhile, but I think they're too small, so I'll be using 3 gallon pots exclusively now. Also need to shorten my vegetative growth phase for clones - I seem to keep them vegging for too long, so the plants become too big for their pots and for my bloom-box....

Plants are growing pretty fast, but almost from the beginning there are signs of deficiencies - paling leaf tips and also the tips of the serrated "teeth" along leaf edges. Leaf edges curling up.... the leaves are too light green in general, and other signs of defs I cannot, for the life of me, make sense of.

Pretty early on the pH starts trying to escape the earth's gravity. It goes over 7 and keeps rising. I was pH-ing my irrigation water to 6.2, then to 6.0 (using GHE pH down - nitric & phosphoric acids), with no effect. Tried flushing the big ones that are in bloom - flushed a 3 gallon pot with 9 gallons of RO water, and the pH wouldn't budge. Stayed at ~7.3. I pHed my water to below 6 for the last gallon of water to which I added a mild nutrient mix - runoff pH was not impressed.

I've spent days searching the net & reading about pH and other issues, but I'm still clueless. How do I bring the pH to reasonable levels?


Jerry The Mouse

New Member
Yuuup.....lime =D 6.5


New Member
I've heard that dolomite lime is for bringing pH up. Also heard people mentioning that it could be used to stabilize pH.

Anyways, it's impossible to buy it in my country, and I've searched...... hell, I'm stuck without perlite now - can't get any anywhere. I think that ordering dolomite on the web, by mail, is impractical - it weighs a lot, and it would draw attention to my little show.

I'm using chemical pH testing kits, and I get the feeling they are pretty reliable. Not the crappy 4-9 ones, I use kits for aquariums that have a significantly smaller range and are more accurate.

Aren't there any other agents / amendments I can add to the soil to buffer pH? I've heard about aluminum sulphate, but aluminum is toxic to humans, innit?



New Member
Organic pH issues

I hear a lot of people asking or talking about the pH of their organic soil mix or organic nute solution and how they might correct or adjust it. pH in organics is not an issue like it is in synthetic growing.
The best place to settle the pH issues in organics is within the grow medium. A medium rich in humates (humus) is the place to start. Humates work to "buffer" the pH of organic mediums and the nutes you pour (or mix) into it.
Humates come from compost, worm castings and bottled humus. If you use a peat based medum, use dolomite lime to raise the pH of the acidic peat. Dolomite should be used in any soil or soiless medium to provide magnesium and calcium. But since we are talking about pH here, I'll mention dolomite lime's pH correction benefits.
A medium of coir has a pH near neutral (or 7.0). But humates are still neded to allow uptake of organic nutrients that are outside a near neutral pH range.
With an active medium rich in humates you can pour in nutes like Pure Blend Pro, Earth Juice and guano teas way outside the optimum pH range without worry. The humus will allow the nutes to be taken up through the roots, even at such an extreme pH reading.
So throw those pH meters away folks and enjoy the ease and safety of organic gardening.
I've read somewhere already that humus can stabilize pH, though it does not seem to be working for me. Worm castings are a type of humus, right? But I think I'll get me some bottled humus. Was also thinking of using peat moss to counteract the rising pH. And dolomite.... gotta keep looking....
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New Member
don't worry too much about what's going in until you find out
what's coming out. You shouldn't change the ph of your
distilled water unless you want to specifically change the
ph of your soil.
It's not just the ph you want to concern yourself with when
adjusting ph, but also the tds. The higher the tds and the further
the ph is from the ph you're wanting to move it from, the more the
ph will move.


If your soil ph was 6.0 and you wanted to raise it to 6.5.
You would get it there more readily by adding a solution that
has a tds of 1,000 ppm and a ph of 6.8 than you would
with a solution that has a tds of 10 ppm and a ph of 8.0.
The low tds of the 8.0 solution won't change the ph of
your soil much.

Stronger acids give up more protons (the positively charged parts of atoms); stronger bases give up more oh- (hydroxide). Neutral substances have an even balance of protons and oh-.

Knowing what's going in tells you the ratio of protons to hydroxide, but what you need to know is how will that change the ratio in the larger picture (your soil). The higher the tds is the more protons and hydroxide you have to change the ratio of positively charged atoms, provided that the ph going in is different than what's there already.

An example of this is when you put a couple drops of ph down in distilled water you will see quite a change in ph because there were no protons or hydroxide in the water to begin with.
On the other hand if you put a couple drops of ph down in water with nutrients added, you'll see next to no change at all in ph because there is a lot of protons and hydroxide already in the water keeping the ph from moving very easily. You'll need to add much more ph down to get a change and that is what will make a noticable change in the ph of your soil.

When using distilled water that has a tds of 0 ppm the amount of ph up or down you're using to change the ph is not really worth messing with. By the time it gets in your soil it will be diluted so heavily it won't make a difference. Just make sure you're dictating the ph of your higher tds solutions (nutes) going in.

If you want to use distilled or very fresh water to change the ph of your soil, don't even test the ph of what's going in it will just freak you out. You'll need it to be very far from 7.0 to make a change. So, just add a small amount of ph up or down and keep testing your run off until it's 6.5 - 6.8.

Make sure when you want a really accurate test of your run off that you use low tds water because it will readily take on the ph of your soil. When you add nutes it's not the best time to check the run off.

Good luck and skill growbaby. I think you'll love the world of organic soil growing.

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New Member
I've had success lowering the PH by adding some coffee grounds. It's organic and it's acidic. Start at the next watering and apply a 1/4 inch to the soil and water it in. Check and add more if needed.


New Member
Really quick in a few words as my first post and for my first grow ever.. What I have learned in a few days is. If I'm wrong please correct me..
Baking soda (Ph Up)to raise it & Lime juice (Ph Down) to lower it..
That's if you can't find any Dolo lime.. That's what I just sprinkled on top of my soil.. I want to transplant but I've topped it and started to LST it yesterday.. But I've read a few forums and I understood it like that but i might be wrong..
I'm always HIGH. (i mean MEDICATED) LOL!!!


New Member
I think you should adjust the pH of the solution after you add any nutes. The water itself is unbuffered and its' pH will change with very little acid or base added. The nutes can really change the pH by a lot. I had 7.1 rain water and after adding all my nutes it was pH 4.5!

Also, potassium hydroxide (KOH) is probably healthier than baking soda to adjust the pH up.

Good Luck!
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