# Potassium Deficiency?
**URL:** https://autoflower.org/t/potassium-deficiency/264
**Category:** Q&A Grow Help
**Tags:** indoor, autoflower
**Created:** [March 3, 2026, 1:06pm UTC](https://autoflower.org/t/potassium-deficiency/264 "2026-03-03T13:06:48Z")
**Posts on this page:** 12
**Page:** 2
### Author:  [@PeaceLoveBuds](https://autoflower.org/u/PeaceLoveBuds)
#### Post date: [March 10, 2026, 11:05pm UTC](https://autoflower.org/t/potassium-deficiency/264/21 "2026-03-10T23:05:10Z")
I bought mine on Amazon along with a connector for hose bib to 1/4 tubing so I could use it out here by the grow room. Makes it super convenient if it’s just for growing purposes anyways
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### Author:  [@Entombed](https://autoflower.org/u/Entombed)
#### Post date: [March 11, 2026, 5:47am UTC](https://autoflower.org/t/potassium-deficiency/264/22 "2026-03-11T05:47:48Z")
Ah no unfortunately. The thing is if your water is 300ppm and your nutrient feed chart says 500ppm, well you only have 200ppm to give. If you did the full 500 dose plus the water then you’re giving the plant 800ppm.
Make sense? Plus all that calcium is gonna throw other stuff out of whack. I don’t think a nute change would solve it.
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### Author:  [@Molobolo](https://autoflower.org/u/Molobolo)
#### Post date: [March 14, 2026, 6:02pm UTC](https://autoflower.org/t/potassium-deficiency/264/23 "2026-03-14T18:02:19Z")
I meant stuff that you put on/in the soil like Biotabs. Just wondering because their selling point is that you can’t overfeed since plants only take “what they need”.
I finally received the Apera pen and did some testings :
- Clean water is pH 7.5 EC 650 µS/cm\*, 620 after sitting overnight
- Adding BioDown to lower pH also lower EC, which seems to be expected ?
I take note of everything I do so I checked and noticed I had quite a stupid use of BioDown, with even more variations than I thought as I was never sure of strips results. I tested a few variations :
- Before germination and the first week, clean water + 0.5ml/l of BioDown : pH 5.6 (yikes 😨 ) EC 400
- Third week, clean water + 0.4ml/l : pH 5.95 EC 400
- Fourth week BioGrow 2ml, Alg-A-Mic 2ml (Biobizz’ recommendation) and BioDown 0.3ml : pH 6.00 EC 1230
- Fifth week Alg-A-Mic 2ml and BioDown 0.3ml : pH 6.25 EC 525
There were a few other BioDown variations that I didn’t test. Plants had only two waterings with BioGrow, I found different recommendations for EC but 1200 doesn’t seems that high for veg ? Most waterings had an okayish EC (I think) and the issue started before that, around half of week 3. Maybe I’m misunderstanding how this works but could this come from all the pH variations ? I think I overwatered multiple times too.
They are in pre-flowering right now, this is week 6. Never had any big issues like this, at this rate I’m not sure they’ll make it to the end 😟
**\*** PPM with the 500 scale (US) range from 200 to 615, with the 700 scale (EU) from 280 to 861
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### Author:  [@KingRatt](https://autoflower.org/u/KingRatt)
#### Post date: [March 15, 2026, 12:19am UTC](https://autoflower.org/t/potassium-deficiency/264/24 "2026-03-15T00:19:04Z")
If you are using tap water do not add any calmag products. You will create lockout problems. Plants look hungry. Are these photoperiods?
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### Author:  [@Molobolo](https://autoflower.org/u/Molobolo)
#### Post date: [March 15, 2026, 9:58am UTC](https://autoflower.org/t/potassium-deficiency/264/25 "2026-03-15T09:58:05Z")
Yeah I don’t use any calmag, the only “extra” nutrient I use is Alg-A-Mic. These are [Auto Cinderella Jack](https://dutch-passion.us/cannabis-seeds/auto-cinderella-jack) by Dutch Passion. I thought they were hungry when it started, gave them two waterings of BioGrow but it still kept spreading. I’ll give them flowering nutes at the next watering. Recommended EC for flowering is generally 1.5/2.0 I think I should start with 1.5 ?
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### Author:  [@KingRatt](https://autoflower.org/u/KingRatt)
#### Post date: [March 15, 2026, 8:32pm UTC](https://autoflower.org/t/potassium-deficiency/264/26 "2026-03-15T20:32:32Z")
Yes always start on the lighter end when feeding.
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### Author:  [@KingRatt](https://autoflower.org/u/KingRatt)
#### Post date: [March 15, 2026, 8:36pm UTC](https://autoflower.org/t/potassium-deficiency/264/27 "2026-03-15T20:36:49Z")
I recommend investing about 10$ in some General Hydroponics ph testing liquid. It’s 100% repeatable and always accurate. I don’t trust meters, because they don’t tell you when they need to be calibrated. I use to use a meter and calibrated monthly, and have way better results since switching to the drops.
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### Author:  [@Molobolo](https://autoflower.org/u/Molobolo)
#### Post date: [March 16, 2026, 10:41am UTC](https://autoflower.org/t/potassium-deficiency/264/28 "2026-03-16T10:41:57Z")
Yeah I use mineral water as reference to check if it’s still accurate before tests, plus I think the EC combo should help in the long run. Strips obviously didn’t serve me well, I thought liquid would be the same but it’s nice to hear it’s not, I’ll keep that in mind.
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### Author:  [@KingRatt](https://autoflower.org/u/KingRatt)
#### Post date: [March 16, 2026, 3:57pm UTC](https://autoflower.org/t/potassium-deficiency/264/29 "2026-03-16T15:57:00Z")
Not all ph liquids are the same, some are for drinking water, some for plants etc. General Hydroponics has the best product for our needs that I have found.
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### Author:  [@TomBombadil](https://autoflower.org/u/TomBombadil)
#### Post date: [April 17, 2026, 10:43am UTC](https://autoflower.org/t/potassium-deficiency/264/30 "2026-04-17T10:43:08Z")
calcium locks out k and mg
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### Author:  [@Cannaficianado](https://autoflower.org/u/Cannaficianado)
#### Post date: [April 17, 2026, 9:27pm UTC](https://autoflower.org/t/potassium-deficiency/264/31 "2026-04-17T21:27:34Z")
This looks like a ph issue to me.
Either that or if you’ve fed, some of your nutrients have precipitated and become unavailable to the plants. This seems like a ph lockout to me.
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### Author:  [@GasPlease](https://autoflower.org/u/GasPlease)
#### Post date: [April 17, 2026, 11:20pm UTC](https://autoflower.org/t/potassium-deficiency/264/32 "2026-04-17T23:20:57Z")
> [@TomBombadil](#):
>
> calcium locks out k and mg
I didnt read every detail but this makes the most sense to me after scanning. OP says he has very hard water(calcium) and plants show K and Mg deficiency signs.
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