Do I need Cal/Mag?

Hi smart people,

I have a crap shoot of plants started from seed, they are at variable stages due to the autoflower genetics present in the seedlot. The plants I want to concern myself with are coming into flower now/have been for a few weeks. Zero deficiencies, look healthy and robust. Seeded November 1, most are in full flower but some are just starting. Sown in peat, 3 gal pots, I’m using General Hydroponics as that was what was suggested to use at the time (what do you feel is better?). I attached two pics, one just starting and one further along.

Do I add Cal/Mag prior to visible deficiencies in lower amounts or do I wait for visible deficiencies to present? I feel I should add a lower amount now, but our water is high in bicarbonates so perhaps the plants are receiving enough cal/mag already? The water test shows 106.7 Calcium and 40.85 Magnesium (ug/mL). Can I push yield this way?

Thanks so much for your help.


I am a few weeks behind you (11/15) and just entering flower, I did not use calmag until I could see visible deficiencies and even then I started at 1/4 strength. However unlike you my city water lacks in calcium so I do add calmag with all my waterings once I notice it’s needed, I grow in FFHF so it’s generally not needed till weeks 4-6…and I am also using general hydroponics and I like how simple it is to work with if using it in smaller doses. Your plants look great btw

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When I saw this, I knew it was time to start calmag, imo keep it simple, if they’re thriving let em continue


me ive just started using calmag this grow. i start adding it once i start feeding at day 30± im in ffof soil so i dont need to add anything til then. but i add it every watering. i use 1ml/L. as recommended by my hydroponic store.


Same here. Around week 5-6 I supplement a but of calmag myself. Starting out low and working my way up if I see deficiency. Also start of flower happens to be normally when u see deficiency start.

Your plants are a nice deep green. So be sure to pH ur calmag solution i to appropriate range for ur medium before pouring.


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 (photo or auto)
-Age of plant
-Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF
-Vessels: Type and capacity of container (fabric, plastic, etc)
-PH and TDS of Water, Solution, runoff (if Applicable)
-PPM/TDS or EC of nutrient solution if applicable
-Method used to measure PH and TDS
-Indoor or Outdoor if indoor, size of grow space
-Light system List brand and wattage/spectrum
-Actual wattage draw of lights
-Current Light Schedule
-Temps; Day, Night
-Humidity; Day, Night
-Ventilation system; Yes, No, Size
-AC, Humidifier, De-humidifier,
-Co2; Yes, No

If growing Hydro some additional questions:

-DWC? RDWC? Autopots? Ebb and Flow? Other?
-Distance of liquid below net pot (DWC)
-Temperature of reservoir
-TDS of nutrient solution
-Amount of air to solution

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


Nothing wrong with the gh products. In racing we say run what ya brung. There is a cheaper more simple alternative but what you’re using is ok

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Is that what this is