water cal:mg ratio is 10:1 - how much epsom do I need ?

R

RUFUS HOUND

Member
hi all, I keep getting mg deficiency and on checking my water report it had the following results

Averages
CaCO3 - Calcium Carbonate 122.23 mg/l
Cl - Chloride 9.74 mg/l
Alkalinity (HCO3) 64.92 84 48 mg/l
Ca - Calcium 41.73 mg/l
Mg -Magnesium 4.36 mg/l
Sodium 9.41 mg/l
Sulphate 61.99 mg/l

I believe the calcium : mg ratio should be 3:1 but its 10:1- can anybody help with how much epsom salts would be required to bring my cal:mg ratio to 3:1
 
Star Dog

Star Dog

Well-Known Member
Maths isn't my strong point but I'll have a go... If i got this right you would boost the magnesium from 4.36 mg/l to 13.6 mg/l that equals 3-1?

Divide the 41.73 mg/l by 3 = 13.6 mg/l = 3-1?
 
R

RUFUS HOUND

Member
hi and thanks for your help - Thats about as far as I can work out, I need 10ppm approx to bring the ratio to 3:1

I guess I could sprinkle a few grains of epsom in the water until the ppm increases by 10ppm
 
Rurumo

Rurumo

Well-Known Member
In practice, those cal/mg ratios don't really mean much when growing cannabis, esp under LED. Excess Ca is one of the major nutrients that causes lockout, along with excess K, but mg is more lenient. You find people add a wide range of epsom salts with good success. Even a 1:1 ca/mg ratio is unlikely to cause problems. What nutrients are you using OP? With a 2 part nutrient line you can adjust the calnit down a bit with 40 ppm in your water already, and will need a small amount of added epsom salts, depending on which nutrient brand you use. You might only need to add .5 grams of epsom per gallon.
 
Star Dog

Star Dog

Well-Known Member
My truncheon only measures a minimum of 0.2ec/100ppm if I need to work out anything less I'll make up x amount 0.2ec then dilute it say 10x for 20ppm.

If you know the purity of the product you can work out the ppm from that...example 1g of 99.9% pure to 1ltr = 1000 ppm +/- a few ppm
10% purity would be 10g per litre for 1000 ppm.
 
R

RUFUS HOUND

Member
Rurumo said:
In practice, those cal/mg ratios don't really mean much when growing cannabis, esp under LED. Excess Ca is one of the major nutrients that causes lockout, along with excess K, but mg is more lenient. You find people add a wide range of epsom salts with good success. Even a 1:1 ca/mg ratio is unlikely to cause problems. What nutrients are you using OP? With a 2 part nutrient line you can adjust the calnit down a bit with 40 ppm in your water already, and will need a small amount of added epsom salts, depending on which nutrient brand you use. You might only need to add .5 grams of epsom per gallon.
Click to expand...
I use chempak no. 2 veg no. 8 flower, that's it apart from epsom
 
R

RUFUS HOUND

Member
Star Dog said:
My truncheon only measures a minimum of 0.2ec/100ppm if I need to work out anything less I'll make up x amount 0.2ec then dilute it say 10x for 20ppm.

If you know the purity of the product you can work out the ppm from that...example 1g of 99.9% pure to 1ltr = 1000 ppm +/- a few ppm
10% purity would be 10g per litre for 1000 ppm.
Click to expand...
Assumed pure but will see if packing has % anywhere
 
Star Dog

Star Dog

Well-Known Member
Billy the Mountain said:
I'm not sure what that product is, obviously not just magnesium sulfate; every bag of epsom I've purchased is 100% pure

Anything with 100% purity is 1g-1ltr = 1000 ppm or 2.0 EC

- That's incorrect; 500ppm/1 EC only applies to sodium chloride

View attachment 5143724
Click to expand...
Thanks for that I'll know what to look for in future.

I still stand by 1g = 1000 ppm or it has done with 99% mpk, salt and calcium something?
a thousand units of each mg/ml
 
Star Dog

Star Dog

Well-Known Member
Yes that's what I'd be looking for I'd make sure it says 99/100% pure.

I thought I'd bought pure epsom but the 10% soluble or 16.6% doesn't make sense, however after a bit googling I find that a dry powder can have water content, according to chemist's magnesium sulphate powder is 50%+ of H202 as in water?
That doesn't make sense to me but it might explain the analysis label as 84% or 90% of the content doesn't exist.
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Chemistry is a interesting subject in general I'd liked to have had some interest in it when I was in school however it wasn't to be.
 
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