Help with using Cal Mag and Jacks

Hey folks! I’m on my first grow and really don’t know much yet. So please bare with me.

I’m growing some autos in coco and using Jacks 321 just about everyday. 1 of my plants is looking light green and I was told to use Cal Mag. Well now I have no idea how to use it.

Do I add the recommend amount to the Jacks or am I mixing a separate batch of just cal mag? If separate do I alternate feeding Jacks one day and cal mag the next? Should I also spray the leaves with or just water the roots?

It seems that there are a lot of post but none that break it down completely. Any help is appreciated.


You should not need to use calmag if your running jacks. The part B (cal-nit) should have all the calcium you need. Do you have a pic of the plant in question you can post ? And what are your dosage amounts and ph for the jacks


How about some pictures in natural light, with particulars of your grow listed?

COPY/PASTE the below list into your forum post.

Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so; Or post
NA (non applicable)

  • What strain, Seed bank, or bag seed
  • Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF
  • Vessels: Pots, Grow beds, Buckets, Troths
  • PH of Water, Solution, runoff (if Applicable)
  • PPM/TDS or EC of nutrient solution if applicable
  • Indoor or Outdoor
  • Light system
  • Temps; Day, Night
  • Humidity; Day, Night
  • Ventilation system; Yes, No, Size
  • AC, Humidifier, De-humidifier,
  • Co2; Yes, No

Always try to upload a clear picture of any issues you may have to allow the community to assist you.

Add anything else you feel would help us give you a most informed answer should be included. Feel free to elaborate, but short and to the point questions and facts will help us help you in a more efficient manner :slight_smile:



  • white widow auto, high CBC from ILGM
  • Coco Coir
  • fabric 5gal pots
  • PH of Water, Solution, runoff (if Applicable)- Jacks 321 ph = 3.8
  • PPM/TDS or EC of nutrient solution if applicable - not sure
  • Indoor or Outdoor - grow tent, 2x4
  • Light system - Mars hydro t1000 x’s 2
  • Temps; Day, Night- 28c with light, 25.8c without
  • Humidity; Day, Night- 65% with light, 45% without
  • Ventilation system; Yes, No, Size…yes, not sure
  • AC, Humidifier, De-humidifier…humidifier on low with light, off without light
  • Co2; Yes, No…no
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3.8 is that correct ? If so you are way to low. Should be between 5.8-6.2


I just checked it again, 4.6.

I am using distilled water so that could be why.

What kind of meter are you using to check the ph?

PH Meter for Water Hydroponics Digital PH Tester Pen 0.01 High Accuracy Pocket Size with 0-14 PH Measurement Range for Household Drinking, Pool and Aquarium (Yellow)

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At your next water/feed bring the ph of your jacks to 6.0 and water till you get a good amount of runoff coming out the bottom of the pot . Your ph is too low and it looks like you’ve locked out some key nutrients.

Your mixing your jacks in this order/amounts

Part A - 3.6 grams per gallon , when that’s fully dissolved

Adding Epsom salt - 1.2 grams per gallon
When that’s fully dissolved

Adding 2.5 grams per gallon of part B.

Let it sit for some time and then take your ph readings and adjust to 6

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4.6 is about right with distilled or RO water. Now you need to add ph up to get it into your 5.8-6.0 target. Cal mag is basically 2 of the 3 ingredients of Jack’s. Cal nitrate and epsom salt (magnesium sulphate).


Another thing you want to check your ph pen To make sure it’s calibrated right.


I use to have a ph meter that looked just like that. I found it to be a lot less stable when it comes to reading PH. I would consider getting a meter that’s a little more reliable like:


I second the Apera meters . Great quality and keep their calibration


So I got some ph up and got my notes to an even 6.0.

Here is to hoping it fixes the issues.


@Watt-Sun @Myfriendis410 @BobbyDigital hey guys couple questions for ya. So i’v been using jacks 321 & CALiMAGic for +10 weeks now, using Tupur CoCo - perlite outdoor in 7gall pots. I ran out of part B few days ago n that’s when I realized I Fd up. I didn’t realize jacks had enough cal mag already. I ordered more part B and they all look good so far. So I should cut the CALiMAGic out or part B n Epsom salts, what would be better, or should I stay with using both like I did for 3 months now?

Just discontinue the cal mag. Keep using Epsom per the 3-2-1 recipe. I would start adding silica, especially for outdoor plants: disease protection, stronger stems not to mention silica is necessary for trichome production. I run silica with Jack’s from the first feeding to the last.


@Myfriendis410 Awesome I will definitely try that out tysm I appreciate it

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Can’t disagree with @Myfriendis410. Drop the calimagic. If you need more cal, add more part B. If you need more mag, add more epsom. Adding silica isn’t as crucial in soil but in coco should be part of your nutrient regimen.


Was reading this post because everyone and there mama is saying go with Jacks123 but i had already bsught FF trio and dirty dozen…im curently adding calmag also…do i need to stop calmag with ff? Appreciate the help in advance.
About to throw out this ff, its more of a headache when already trying to learn enough other more important stuff.