Ph TANKING in my coca coir medium!

Ph of my nute solution versus (about 6-7 ph) my medium is WAY off - usually down to 2-2.5 within 30 minutes.
Using coco coir/perlite. 5/1 ratio. GH nutes. I mix to 6.5-7 ph, one gallon jugs. Upon watering (using 3gallon fabric pots), I can be anywhere from 2-4 ph every single time. These are autoflower, healthy but the soil is SO alkaline, I know the nutes arent getting to the plants like I need them. This is end of week 3 (from seed) w/autoflower and they are SHORT.
I need to obviously elevate acidity CONSIDERABLY in my water in order to get soil to maintain 5.5+ ph. How acidic is TOO acidic? I don’t want to keep using ph up/down to get it right. Rather go organic. Lemon juice? Vinegar? If my ph is sitting in the nutes at about 2, how much lemon juice do you add to a gallon? Ugh… Need some help - first grow!

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You’re already using synthetic nutrients, why not just get the ph adjuster and get it done?

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I have been. I adjust the nutes to 6.5-7, water my veges. and it is down around 2. I guess the main point is - how do I mix the ph to get desired ph within the growing medium. Sorry if I confused. I’m just using a crap-ton of ph adjuster

I don’t measure the ph once I add my nutes. I get the water to about 6.5-7, add my nutes and go from there.

Also, I tried the coco + perlite and didn’t like it. Plants always seemed weak and sluggish. Now I mix half cow/worm manure with half coco, throw in a couple of handfuls of perlite per gallon and continue as normal. I also just use organic fertilizer (fish emulsion) and don’t add anything for the first couple of months as the manure seems to give all the nutrients the plants need.

Recently I seemed to be having an uptake problem, I started adding Superthirve to my water to insure the vitamins and minerals that may be missing from the water. I found out that rainwater and RO water doesn’t have them.

I am new to the autoflowers and am not impressed with their overall size, but I mainline some of my plants and they seem to do a lot better as far as quantity and quality of the buds.

These plants are the same age and the same strain (Jack Herer autos)

There’s a YouTube channel called Hemp in a Pot. They have some outstanding information on all types of grows.

Good luck…


Good stuff - thank you. I do wish I had added compost as an organic source of nutrients, but first grow, so live and learn. Def high-maintenance in ensuring proper nutes are present without the compost. I’ll check out the youtube channel - absorbing as much info from numerous sources seems to help finding the “best practices” across the spectrum. Your two plants - wow what a difference! Short and full, tall and lanky. What do you attribute the difference?

Did you wash your coco and perlite before hand…
Most coco needs to be washed before use…


That’s probably why you didn’t like it. The nutrients will change ph once added. Doesn’t matter what you start with, just what goes in. Especially with something like coco. Your ph should be something like 5.8ish.

You’re adjusting to too high of ph. When you say “it is down around 2” what do you mean?

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oh yeah! Ph is always the last thing I check too. Especially in a soiless medium! Virtually zero buffering.
Its the same as liquid hydro…

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A ph of 2 is basically pure lemon juice! That plant would pucker up and just die on the stick. You cannot have a ph of 2 and still have a living plant. That is super acid.


Worst I’ve had was 4.5 ph and plants were super angry…
I try to float around 5.5 to 6.5 depending on what stage of growth I’m in…
Huge swing but is easily handled in hydro…
Mind you , I only grow in water…
No media…
Just neoprene collars and water…

It’s called mainlining or mainifolding.

Update: as a newbie, learning alkaline and acidic readings, I totally misread the gauge. I have been mixing my nutes to a 5-5.5 ph, but after watering in the coco, I end up with 6.5-7.0 ph, far too alkaline, if my research is correct. Do I go much lower in ph? Worried about burning stuff up, but I want the nutrient uptake to be more effective. Sorry for the confusion - i’m confused, so… :smirk:

Yea, i was totally misreading the gauge. I have been mixing my nutes to a 5-5.5 ph, but after watering in the coco, I end up with 6.5-7.0 ph, far too alkaline, if my research is correct. Do I go much lower in ph? Worried about burning stuff up, but I want the nutrient uptake to be more effective. Sorry for the confusion - i’m confused, so… :smirk:

No. Ideally you will be around 5.8 in and out. So after mixing your nutrient solution measures 5-5.5 and you apply enough to get runoff, runoff measures 6.5-7?

What are you using to check ph? And how often are you feeding?

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Anywhere from 5.8 to 6.8 is nice. Having some ph swing is a good thing because it allows access to nutrients on the outer edges of the scale. Have a look at a ph chart for cannabis plants to understand the relationship of ph to nutrient uptake. What you must understand isnthe nutrients on the opposite ends of the scale are there by design, as they are needed in very small amounts by the plant. They are, nonetheless, needed, therefore, the ph swing is a good thing. Hope this makes some sense to you.

@dbrn32 They are about 18 days old, have been hesitant to wet to the point of runoff this early, but I will generate enough solution to do exactly that. I now remember in my research that runoff is the most accurate measurement of ph. I am using a two prong meter with light, oh and moisture modes. I will respond to your last question once I get some runoff. Thanks for the advice! :pray:

Then that is also contributing to your issue. Coco misbehaves when it gets dry. You should be feeding to good amount of runoff every time.

Growing in coco is nothing like growing in soil.

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18 days old barley needs nutrients it’s still feeding off the seed leaves.

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Ok, got nutes mixed, with ph pegged at 5-5.5. After saturating each plant, upon measuring runoff, I am sitting between 6.5-7.0 ph.

Mix up enough solution to keep pouring through until you get to around 5.8-6 for runoff. This is is called flushing. Once you get to that point make sure you are feeding at exactly 5.8 and getting a good amount of runoff every time you feed. Also make sure you aren’t letting coco completely dry out between feedings.

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