Hello, so I use tap water in my rdwc, where I live we have very clean tap water ppm from the tap is about 60 I’m about to flip my current grow to flower. This grow I have not used calmag at all as the last couple of times when I have put it in I have seen a negative effect on the plant. Where I live I can check the water quality for my area which shows the results of the most recent micro biological analysis and I can see that there is calcium and magnesium in the water. Am I making a mistake not using it? The plant looks very healthy. What is the biological significance of calmag?
morning Takumi…my understanding is that calmag helps your plant take in nutrients from water … the less TDS in your water, cleaner it is like distilled or RO, the more you need to add calmag to help with nutrient uptake…if you are not seeing any issues with feeding then IMHO you don’t need it
There are several, I only know a couple, calcium making strong cell walls resistant to disease, magnesium used in making colors terps and secondary metabolites. Highly important for quality buds.
Calcium is a secondary macro nutrient, very important in nutrient uptake, cell wall development and overall metabolism rates.
It’s very important and it’s also very important it’s not over used, it will lock out many other nutrients.
I abandoned calmag a couple years ago.
I use Reverse Osmosis filtered water so it starts out with less than 10ppm.
Never had any issues since. I am not alone here on the forum in this regard.
I know calmag has a strong following but personally I think its overused most of the time.
Just my opinion which is not worth a lot. 
Absolutely. A commonly cited solution to nearly every problem is “give it some cal/mag” in some weed forums. It appears here from time-to-time too from newer members who have come from other forums.
I’ve rarely seen an actual cal/mag deficiency and I’ve never seen a cal/mag excess.
Yep. My first question now is “What is your pH readings” Nearly all problems start here.
This is exactly the point I was getting at haha,
Everyone is always so quick to jump to cal mag, I use RO water and never use cal/mag.
Any good cannabis soil and nutrient line will understand the importance of calcium.
Exactly. Every line I have tried is full of calcium. Currently using Jacks and part B is Calcium and Nitrogen. Epsom provides Magnesium. Other lines cover it too. I know some use it so they can pH adjust the water for living super soils since you cant adjust low ppm water. But I am not sure I see the wisdom of that either. But then I am just a hillbilly banjo picker.
Im guilty of jumping on the cal mag train. I threw mine out after reading between the lines of @MidwestGuy responses anytime cal mag came up 
I’m not going to say that cal/mag is useless. Please don’t get me wrong. It is often needed later in flowering when demand is high and original soil levels are depleted. When I used cal/mag I started applying it once in flowering.
I’d guess part of the reason it is cited so often is that it’s pretty hard to hurt a plant with fairly high levels of cal/mag. Cal/mag is a freebee that causes no harm, but may or may not help.
It does help the tomatoes set fruit better. So I have used it in the garden.
Thanks alot for all the responses, so it seems likely that the nutrients I’m using probably conatin enough if I am not seeing any yellow spots? I will try to use it in a more responsive manner than proactive for a couple of grows and see how it works out.
Always check your pH of the runoff and do a slurry test before you change nutrients. pH issues will mimic all kinds of nutrient symptoms and is far more typical than actual nutrient deficiencies.
Slurry tests are more accurate than runoff
Great thread growmies! I was always quick to Cal/Mag until I learned to ph everything first (learned that here btw)
90+% of of the issues I’ve encountered have been resolved by correcting ph.
I have recently heard just about every soil scientist I follow say this exact thing. To the point of false results. They say always go by the slurry test.
That said I would probably still pull a run off test for my own personal data point. Whether or not I say hmmm after words is another story. Ha
As far as cal/mag, Mother Nature has us covered. Woodash is loaded with it. All you need is a tsp per cubic foot of soil. This is how I re cal mag spent reused living soil. Used soil tends to drop acidic too as the organic components break down. The ash buffers it just like lime. Here is an excerpt from the university of New Hampshire breaking down wood ash:
It’s hydro with a constant monitoring unit that shows pH, water temp and PPM with recorded and resettable highs n lows. Things have been very much in the optimum ranges for almost the whole time on this grow. What do you mean by slurry test?
Its for soil. My mistake.