A couple of questions (cal-mag)

A question from a fellow grower:

this is my tap water profile:
pH 8.8
Total Dissolved Solids (TDS) Est 196
Electrical Conductivity, mmho/cm 0.33
Cations / Anions, me/L 3.3 / 3.5
Sodium, Na 75
Potassium, K Calcium, Ca 1
Magnesium, Mg Total Hardness, CaCO3 3
Nitrate, NO3- N 0.1 (SAFE)
Sulfate, SO4-S 3
Chloride, Cl 6
Carbonate, CO3 21
Bicarbonate, HCO3 145
Total Alkalinity, CaCO3 154

bicarbonate is thru the roof.
virtually no ca or mag
there is na, dunno f thats too much.

how much cal-mag should i add? and ii dont know how much iron there is but i figure there should be enough in the calmag? id like to use bennie safe calmag.

doesnt bicarbonate bond with ca and mag? do i have to compensate?

i could filter the bicarbonate out with an anion exchanger. but i cant find anyone focusing a unit on removing lots of bicarbonate. i dont think i need to ro my water, just carbon out the chloramine besides the anion exchanger, which should get the na to i think…

how bad would it be to leave the bicarbonate

I tend to add cal-mag only as needed or in very light doses half bottle recommendation. Bicarbonate is alkali and a salt which like any nutrient builds up in media which is why I flush several times through any grow in soilless or soil media.

its a salt?

what is the max level of bicarb acceptable in water.

total hardness number i dont quite understand. it says thats calcium carbonate; does that count as usable calcium? so maybe i should only add mag if i dont have to filter out the bicarb?

ps, i am the cusomer who posed the question :slight_smile:

Well my friend I am no employee much like you I am a fellow grower and I go with what has been proven to work well for me over the years without over thinking the math behind it. Most if not all nutrients are defined as salts that is what makes them water soluble and most if not all growers will recommend periodic flushing throughout any grow cycle what your plants don’t use remains in media as salts. In order to reduce the need for flushing media most people feed every third water and always aim for 15-20% run off this actually does some flushing for you while making remaining food in soil avail again to your plant. That being said I still like to flush my media once monthly during veg and 1 week prior to flower flushing is a simple process of washing 3-4 times the containers volume of water ph’d correctly through your soil or media, For this minor hastle I get more stable ph at my root zone and less likelyhood of nutrient lock outs or toxicity happy roots healthy fruits this process happens in nature all the time rain showers :slight_smile:

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This is what most people think of as salt, this is the main thing in table salt, and this is not good at all for cannabis.

And of what Donald has said, there are different types of “salts”, and nutrients often come in “salt” compounds.

In this definition we are meaning the chemistry definition of a salt, in that it is neither acidic nor alkali, the neutralization of acids and a bases(alkali) and composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge).

This is true of table salt as well, it is a compound of sodium and chlorine, creating sodium chloride, it is just sodium is not a needed nutrient at all, however chlorine is a needed nutrient, although at extremely small levels.


OH! thank you so much for clarifying salts as in chemistry.

i hate our method of schooling. i took two years of honors chemistry and honors chemistry 1 and 2 at university and i dont recall learning that at all.

i still dont know if i should filter out these salts,

since no one will tell me what is too much na or co3; will it improve the quality and yield if i just filter them out.

Well here is the best answer to your question if you are concerned get an RO unit or dilute water with distilled water as for cal-mag as I said use lightly or only as needed in hydro it is a must in soil not always.

Hi Donald,
is it safe for me to flush my plants 3 weeks in flower?

im gonna ro. it will help no matter what. so might as well.

Any compound that is not acidic or alkali is pretty much a “salt”, to overly simplify things. As stated above a salt is formed when these acids and bases neutralize each other, they almost always have a “ide” at the end, the suffix denotes a salt compound, like “chloride”, and just because it is a salt doesn’t mean it is bad as long as you are not “over fertilizing”.

For example potassium chloride is a good form of the K in the NPK macro nutrients needed by all plants. They also sometimes end in “ate” like magnesium sulfate, also known as Epsom salts, and you’ll often see people recommending adding this salt to mixtures to help remedy a magnesium deficiency.

This is probably something you did learn but maybe it wasn’t emphasized and you likely just forgot about it.

Have you read this article?

In general a calcium content in excess of 200 PPM, or 75 PPM for magnesium (in the 0.5 NaCl conversion) are on the verge of excessive. This is 0.4 EC and 0.15 EC respectively. EC is always the same, the conversion is always based off of EC, so if you know the conversion you can always figure out the EC, and because EC is the standard, often you will see people prefer to use EC.

And an excess can cause other important elements to “lock-out” and become unavailable. For example, excess calcium can bond with phosphorous to make calcium phosphate, which is not very soluble and therefore not very available to the plant’s roots.

I’m not sure about your numbers, because a 0.33 EC should be more of a 160 TDS, not 196, maybe your conversions are in the 700 scale, but I’m not sure.

RO and starting knowing exactly what you put in your water is a great place to start.

Happy growing,


the article states nothing more than generalities. which get said over and over again. ive bought two books and read the ilgm bible. again ultimately mostly generalities.

if i went straight off of ppm or tds everyone would say my water is fine. but the actual profile shows a very different story.

i would pay hundreds for a book that actually gave real perameters on nutes and showed the science to prove it.

i would like to say im getting the best, most informative response here than any other forum. i will certainly contribute in the coming months and years.

Well I gave you some specifics, lol. I might be able to get back to you with some specifics on sodium and maybe some others.

when i add ph down the caco3 is changed right?, what particularly happens?

Nicko I am sure you are over complicating a issue because your chemistry background is making it hard to accept a very simple answer. RO is always the best option and most people are budget minded and want a simple answer which doesn’t put them out of wallet that being said books are written that are dumbed down to not confuse a simple fact. Cannabis is a weed which will put up with lots of abuse and still grow given right conditions it will thrive.
If you look at growing as too riggid a thing you will set yourself up for disappointment every plant is different every gram of medium is different it is a series of rolling with and adjusting to constant variables there is no perfect formula for every plant. There is only a constant learning curve and faster recognition of symptoms and results.

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You can Flush 3 weeks in flower if need be if you choose to as you are improving root environment many scrog and don’t have the option just remember to ph your water correctly and feed after flushing since your plant is bound to be hungry and flushing removes bulk of nutes remaining in the soil.

@ Donald , thank you

Where did you get the numbers for your tap water profile? Again, I am having some difficulty making sense of it, some things are not adding up, or don’t seem to make sense.

Something to consider about the sodium, is where is it coming from and in what form, it isn’t likely just sodium, if it is sodium chloride, then, as I said above, there really shouldn’t be much at all, and many plants will not tolerate even levels as low as 50ppm or 0.1 EC of sodium chloride. However sometimes some sodium is unavoidable – as often some of the plant’s required nitrogen comes from sodium nitrate.

As far as what happens to the CaCO3, this will depend on what your “pH down” contains. Most “off the shelf” pH down is primarily composed of phosphoric acid, and may contain some citric acid and maybe even some acetic acid, and then others might use sulfuric acid. As I stated above, it is the way these bases and acids bind and neutralize each other, creating the end result of a salt compound. And this is strange that you are having a hard time with this, or seem to have forgotten it, as this is almost the most basic of chemistry and one of the first things they teach you in chemistry, this is pretty much how all chemical compounds combine, this is chemistry though and through, I’m sorry but this is really not making sense, this is chemistry. Acids and bases is like lesson number one in Chemistry 101.