Struggling with Promix HP

I’m doing a SOG with 25 1-gallon pots, using ProMix HP.

The plants are yellowing. I have set the pH for the water+nutrients (I am using Jacks 321) for 6.0, but I suspect this is not what the plants want.

What pH should I be setting my water/nutrients for?

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S what is your runoff ph and ppm

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6.4-6.8 and shoot for 6.5


@Myfriendis410 is a Promix grower. I believe he runs pH at 5.8 to 6.0. Promix is closer to coco than it is soil.


I pretty much shoot for 6.0 on everything: seems to do well for me.

Yellowing could be overwatering but pictures would be helpful.

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Oh my bad, im just so used to mixing peat with my soil and wasnt quite awake yet…sorry its been a minute since ive used straight promix due tounsteady availability

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There is a good series from promix on YouTube, may be worth checking out to help understand how best to use it.

Okay, so I finally had a chance to get answers to all the questions.

I upped the pH of the feeding to 6.5. PPM of feed is approx 750. I’m using Jacks 321, CalMag, and General Hydroponics silica.

Runoff was 6.4, PPM was 1100. (!)

I think my feeding pH was too low - I was at 6.0.

And … this is ProMix BX, if that makes a difference. I’m not sure how I ended up with BX … DOES IT MAKE A DIFFERENCE?

Pictures below.

Any/all advice gratefully received.

@dbrn32 - can you point me to it? I searched, I don’t see anything that looked relevant?

@Newt uses ProMix HP.

It looks like it does. Promix HP is “high porosity”. You may need to treat the BX more like soil than the HP.

BX is a soilless peat mix like HP without all of the perlite. PH should be 6.0 nominally.

Jack’s does not need cal mag. It is composed of calcium nitrate and magnesium sulfate (among other salts) which satisfies any need for cal mag.

PH is high, runoff TDS is fine.

Plants are showing N def and likely due to low feeding concentration. Leaves will not recover so look to new growth for signs of improvement.

What lighting is being used for them?


Literally the Promix YouTube channel, linked below



Thanks for the tip on the CalMag. I’ll stop. :slight_smile:

The lighting is 2 HLG LEDs, each light is 260W Rspec, at about half power.


I’d bump the lights up to around 75% and up your nutrient load to 900-1,000 ppm.


Well, guys, this has been a constant struggle. I am not sure what I’m doing wrong.

I mean, I know some things I did wrong, but now the whole grow has just gone to crap.

First, the pictures:

The yellowing on the bottom never really went away, and has just progressed. I changed pH to 6.5, and that seemed to help for a bit, then I screwed up the lighting, and the whole thing just went downhill

I got UV lights to boost bud production, and set the damn timer wrong, so basically the lights were on for three days straight (alternating between LEDs and the UV lights). I think this entire crop has hermed? Is this what it looks like? (I’ve never seen this before.)

Or are these just really prominent brachts? Because I don’t see many pistils anymore…

Should I just trash it all and restart, or let it finish out and get the seeds, or? Any and all suggestions gratefully welcomed.

I’m also going to get ProMix HP for the next round. I think using BX was a mistake, and it’s retaining too much water.

ARGH. This sucks.

(The good news is that the other tent, which is Maui Wowie in RDWC, is going like gangbusters.)

@Myfriendis410 @Newt @dbrn32 - Any suggestions?

I’m getting concerned that these might have turned male (they were clones from a feminized seed) and will soon blow pollen all over my basement?

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They won’t turn male but can produce male parts in addition to female parts. This would be called hermaphrodite. Do you see any pollen sacks or stamen?

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