Jacks 321 Hydro discussion, questions, tips, etc

I did a quick search and couldnt find a Jacks specific thread, so Im starting one. Im mainly interested in the hydro applications, but feel free to toss in anything you want on this general subject or even bring up other nutes - but - Id prefer to keep in mostly about Jacks or the other brands that use the same basic formula. Still, Im not a “stay on topic” fanatic, so feel free to wander… :slight_smile:

I just switched to Jacks in an AAA (air atomized aeroponic) setup, and am loving it so far, but this is all new to me. There are a ton of videos and looooong threads on other forums, but I wanted to get the OG family take on this stuff.

I have to run, but I want to start off by asking for any input from anyone running Jacks in hydro and get your feed back on three main things.

  1. PH - do you mess with it and what range to you run?

  2. Concentrations - EC, PPM or what ever.

  3. Mods or adds - Do you do the basic 321 or change things up or add extras or?

Gotta run…

Im gonna tag a couple of folks who have mentioned Jacks recently… I Know Im forgetting several…

@Howard.Crane @SuperiorBuds @SquirtleSquad @ReikoX


@paintedfire420 this is your world

  1. I don’t mess with it, unless things are very off. If humidity levels, heat, or other factors cause the solution to change too much in any parameter, I deal with it by doing a rez change. Probably a habit from my old reef-tank days, where they say “the solution to pollution is dilution” lol. Depending on my water source and how diligent I am at measuring, pH tends to fall between 5.8 and 6.1 after mixing, and I just run with it.

  2. I’ve had very good success running at 1.4 E.C. from start to finish in the past, but I’m now using 1.6-1.7 E.C. and well pleased so far. Then again, I’m not currently growing my favorite Haze, which requires a much lower concentration.

  3. Almost never. I’ve used potassium silicate in the past, and would prefer to now, but it’s more hassle than it’s worth to me. I may start to experiment with reduced N in late flower once I’m well established in my new routine. I’ve tried bloom boosters at various points in the past, and did not find doing so to be worthwhile in my situation.

  1. PH - 5.8… No need to adjust when running Jacks at the right dose, and with tap water.

  2. Concentrations - Usually 1/2 teaspoon of Jacks pro, and a half teaspoon of calcium nitrate per gallon(1300 ppm). Dropped it down to 1/4 teaspoon of each…So far, so good!(650 ppm).

  3. Mods or adds - Straight up Jack’s & Calcium nitrate… Nothing else is needed, well maybe a drop or two of Superthrive in veg.

I Change out nutes every 7 days… Religiously. :wink:


I use the Dynamic Duo for my soiless mix, 1/4 tsp every watering, every 3 day.
I ph my water to 6.3 to 6.7 then add Jack’s, just cause my water is in the 8’s so I gotta bring it down.


Are you running it in a reservoir? Does the ph stay stable or shift back up?


ph 5.5-6.2
seeds/clones-1 ec. everything else i start at 1.8 and adjust as necessary.
as for additives, i run fulvic acid (dry at .15 g/gal) and southern ag garden friendly fungicide at .2 ml/gal (hydroguard substitute. same active ingredient, way more concentrated, way cheaper). i also run mono potassium phosphate and potassium sulfate as needed in varying amounts, and growsil (dry amorphous silica) at .05 g/gal in veg.
you mentioined that you are running aero. i suggest looking into a product called haifa cal prime as a substitute for the standard calcium nitrate. the normal stuff works in hydro, but its not ideal. i can elaborate if you want, but the short version is that its slightly more concentrated with very little ammonia content and helps keep your res more stable for longer. cost difference is negligible, and it runs at 2 g/gal as opposed to 2.4 for the standard calcium nitrate


Sorry all - Im a bit under the weather, but want to reply to a couple of things - more later…

Not sure who you are asking, but in my case, the PH is rock solid. It doesnt move unless I force it with PH UP or Down.

Now, keep in mind my setup is drain-to-waste - NO re-circulation at all. The nute water never touches a root until after it goes through a spray nozzle. What ever the roots dont drink, gets tossed or fed to my wifes plants.

I would normally expect the PH to be perfectly stable in a non-re-circulating rez. There should be nothing in the rez to cause the PH to change over time - BUT - with every other nute I have tried, the PH ALWAYS climbed in the rez.

But with Jacks, it doesnt change until I make it change.

I have questions and comments for almost everyone else, but I am going to go to bed after one more question.

Actually more of a clarification about PH.

The Jacks people recommend leaving the PH where ever it ends up - even as hi as 6.5 or more - even when running hydro. They dont recommend adjusting the PH at all - just mix it and forget it. That goes against everything I have read about growing with hydro. The “theory” as I understand it for hydro says you need to allow a PH swing from 5.5 to 6.2 or so, but to for sure stay lower than the mid 6’s.

Some of you seem to be on board with the mix-it-and-leave-it thing and others not?

Im so used to having the PH constantly climb, that I have always ended up with a large PH swing. Im tempted to try just mixing it and leave it alone.

Do you guys think its ok to just let the PH fall where ever when using Jacks in hydro?


IMHO,… I dont think its “ok” to let the ph fall wherever… :neutral_face:

If I use unfiltered well water, my ph is all over the freakin’ place… :expressionless:

When I run city tap water, my ph stays right around 5.8 … and will drift(5.7-5.9), but only slightly, which is COMPLETELY normal. :slight_smile:

Jack’s Hydroponic nutes are PH buffered, and if you have really good “tap water” then you do not have to adjust the ph at all, or add anything like ph up or down… I sure dont. :relaxed:

You want your plants right around 5.8 at all times… Its a must. At 5.8 your plant gets everything it needs… Too high, or too low… your girls will have deficiencies, and FAST! :wink:

The secret to a stable ph is to run clean “tap water” and not filtered, or else you will need to add cal mag etc… And then your chasing down problems left and right… :tired_face:

Then, it gets tricky, and frustrating, to say the very least. And it fucks with the ph everytime! Cal mag is ok to perk up a sickly plant, other than that, I leave it alone. :wink:

One last thing, ph up or down is EXTREMELY toxic to the root zone… Not good at all for your roots, or your plants!.. “Less is More” … :innocent:


Sorry I didn’t ask very well, but I think you answered it. My tap is 8ph so I was wondering if it would rise back up, which you answered not with Jacks and non recirculating.

What does make the res ph change? Is it airflow.
I’m New to a reservoir and nutrient solutions so just trying to make it correct from the start!



Lots of things can cause your PH to go up or down. Ive been doing lots of mini experiments and testing durring my last several grows.

Keep in mind - this is all based on MY water. YMMV.

My water is well water. Normal EC/PPM is very low. EC is usually under 100 or about 50 PPM on the 500 scale. However, it has a fair amount of carbonates in it, but its not really hard or soft water and its un-treated.

Here is a list in no particular order.

  1. Any agitation or aeration of my water causes the PH to go UP - fast. Once things have settled down to equilibrium, the PH wants to settle at around 6.7-7.0. It doesnt matter where it starts, if its aerated or agitated, the PH will rise to that range in just a few minutes to a few hours depending on the starting conditions AND the water temp. Higher water temps = higher final PH. Colder temps lower the final PH to some degree. It has to do with dissolved CO2 and the carbonates in the water forming carbonic acid, which lowers the PH. As the dissolved CO2 leaves the water, the carbonic acid level goes down, which means the PH goes UP. That is with zero plants and zero nutes. Just straight tap water.

  2. I Live in a rain forest. Tons of mold, mildew, bacteria, algae etc lve in my water and are just in the air. All of that crap just loves nutes and grows like wild in my water if given any chance. ALL of them raise the PH in my water. This is again with zero roots touching the water. So, any algae or bacterial growth will raise PH. Water temps have a lot to do with it. Water temps again play a part here. Low temps - under 70F can help keep the crap down or at least slow its growth. Over 70F and the crap can explode.

2A) Light is a key thing for algae growth. It is absolutely critical to keep light out of your rez and any pipes, fittings, buckets, etc. You really do need to be fanatical about it or that crap will start growing. Its very nearly impossible to kill it once established without killing the roots.

  1. Roots in contact with nute water change the chemistry of the nute/water mix by using up some of the salts/nutes as they drink. Plus, they give off or exude waste that can also change the PH. In this case, the roots can make the PH go UP or down depending on the details - nute strength, NPK balance, PH, temp, bacterial infections, and other things. Basically once you start re-circulating, the PH can go anywhere - or - it can stay stable if things are balanced and maintained well.

Here is an old chart that covers some of that - but it doesnt take all the factors into account - like #1 or 2 above.

Ugggg more later…


I mix stock solutions with distilled water, pour out 16oz and mix 100:1 so I end up with 112oz.

My target is 2.4g/gal jacks 5-12-26, 0.8g Epsom in one gallon and 1.6g/gal calcinit in the other. So I multiply those by 112 and get how many grams I need to add.

I find I get better results mixing half lb quantities of Jacks so that’s why I make stock solutions. Less likely to stray from the ratio.

It starts getting bacterial colonies around the 14 day mark. There are ways you can remove it but my system is 90gal so it’s basically a res change and 22gal of topoffs. I also don’t mix a perfect 1oz/gal depending on the EC I’m targeting.

EC I get best results around 1.4EC max. This brings me to 1.6EC total with my tap. I do seedlings in a low pressure aero at 0.4EC until a few sets of leaves and gradually bring them up. I need to correct pH at these low feeds, but my tap is 10.3 pH. I use a doser to keep pH at 5.8. Sometimes I let it drift from 5.6-6.1.

Been running Jack’s and chem-gro 5-11-26 for 3-4years now I love it. Clean, super easy, cheap, and plants looks great. I’ve given up on MKP, it causes more problems than it’s worth IME. I had some good results with potassium sulfate but haven’t done significant testing to say it works. It also throws off your K:Ca:Mg ratio. Jack’s 321 delivers 4:2:1 which is ideal for avoiding issues. You can stray a little bit so if you do add those, go easy. Some plants will be fine, some wont.


I think it has something to do with acidic nutrients being used up so the pH rises. It’s a good signal to back off nutrients later in flower once you get the pH drop.

My water is 10.3pH but when I add nutrients it drops it to around 6.0 so it makes sense that as the plant eats those nutrients it will rise back again.

Root rot can cause extreme cases of pH rise. Too little of a buffer is another cause especially amongst bubble bucket growers.


pH is simply a measurement of the available hydrogen ions within a solution. As the plant uses nitrogen the roots give off hydroxyl ions which causes the pH to rise. That is why you see a pH drift upwards in veg in a recirculating system. Later on in flower as Phosphorous and Potassium are used they cause the pH to drop. (I forget the actual ionic reasoning here.)

I mixed up my first batch of Jacks321 last night. I had a bit more RO water left in the grow beds then I had thought so my calculation of total gallons was a bit off, which resulted in a bit lower EC then I had expected.

We’ve had a lot of rain lately so the starting pH of my RO was way up there. Initially the EC was 1.8 and the pH sat around 6.5 but that drifted up to where it is now as I recycled the system a few times (mixing in the left-over RO from the beds).

I wanted the EC a bit lower anyways since I’m starting with seedlings, and I’ll increase the strength once I do a full res change.

I also need to grab my other pH pen and verify the calibration on the Bluelab. I forgot to recalibrate it before I went to bed last night, so it’s possible the pH reading is off.


Have you used Jack’s hydro in soil yet? I’ve been using it in soil and coco and eventually have problems. I’m wondering if it’s the POTASSIUM HYDROXIDE and POTASSIUM SILICATE in the pH-up… since the hydro nutes are buffered it takes a bit of pH-up to get the pH back up to 6.3-6.5 for soil. Maybe I could try a calcium carbonate based pH-up? Or just change to a diffferent feeding program…


I use calcium carbonate or slica to bring up my PH to 6.2 in coco using Jacks Hydro, does not take much of either as my tap is 5.8.

The silica I use is powered Agsil16H from build a soil I use about 1/16 of teaspoon to get my PH to 6.2 a IL will last me a long time @ $20.00 a IL , mixes instantly in water


Ooops! I had a “wake-n-bake” moment… my pH-up has potassium hydroxide and potassium silicate (NOT phosphoric acid)… I’m so embarrassed…

So I may be overloading the mix with too much potassium (silica + jack’s + pH-up), making the leaves slowly develop some interveinal chlorosis like an iron deficiency.
I’ll try using NFTG Olympus Up (calcium carbonate) and see if it helps.

Anyone else use Jack’s/Peters Hydro in soil?


Soil grower here! I have been using jacks 3-2-1 at max strength through veg and flower with absolutely no issues to speak of. I saw no improvement implementing MKP into the flower nutrient regimen, so the basic 321 has been my go-to for nearly every strain I grow. I follow the KISS rule. Keep it simple, stupid. I haven’t seen one deficiency since switching over from the bottled liquid nutes.

Part A also serves as a fantastic aero rooting/cloning nutrient when used at 300-400 PPM with a small concentration of Hormex liquid concentrate. If you keep a sterile res there is explosive root growth.


Thanks for the response @advancedbuffalo. Jack’s is buffered to around 5.8, so what are you using to bring up the pH to an appropriate level for soil? I’m still trying to figure out why I’m getting some light green chlorosis by mid-veg…


What would you consider “clean” tap water? Anything under 200ppm? I’ve been using a 50/50 blend of Ro and tap and haven’t had to use much Ph up if any. I’m not running Jacks yet though but the maxi series. :confused: