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Mixing Magnesium Nitrate and Magnesium Sulfate

MichaelJ

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Joined
9 Feb 2021
Messages
1,690
Location
Minnesota, USA
Hello,
For my current remineralization regime to target a GH of about ~5.5 per 50 liters of water I currently use 4 grams of Magnesium Sulfate and 4 grams of Calcium Chloride.
What I want to do instead, as I am switching over to DIY dosing of NPK as part of my WC water prep, is to blend in Magnesium Nitrate to dose my N for a target of around 30 ppm (this could be 20-25 ppm instead though) and keep my current dose (4 grams) of Calcium Chloride (if that adds up). I want to keep the Ca:Mg ratio to about 2:1 (I am flexible on the ratio).

So my question is how much Magnesium Nitrate and Magnesium Sulfate should I use then?

Based on the info on the Magnesium Nitrate product I am going to use 13 grams (seems like a lot?) of Magnesium Nitrate should reach 29 ppm of Nitrate and 25ppm of Magnesium, which leaves room for 8 ppm of Magnesium from the Magnesium Sulfate or about 1 gram? In other words, for 50 liter of water, adding 4 grams of Calcium Chloride and 13 grams of Magnesium Nitrate and 1 gram of Magnesium Sulfate will yield a GH of ~5.5 at a 2:1 Ca:Mg ratio and 29 ppm of Nitrate.

Also will this mixture still be adding enough Sulfate?

Cheers,
Michael
 
Last edited:

X3NiTH

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Joined
13 Apr 2014
Messages
1,521
2:1 Ca:Mg ratio is unnecessary as plant tissue when analysed by fire assay only yields a ratio of 3:1 Calcium to Magnesium. The solubility of Magnesium to Calcium is 10:1 so it gets transported through river systems quickly and accumulates in the ocean as an opposite ratio of 1:3 Ca:Mg. So the Ratio you should aim for is between 10:1 and 3:1, going for a higher ratio results in no extra benefit for the extra increase in conductivity and hardness.

The reason why the Magnesium Nitrate weight looks excessive is that it’s a heptahydrate and as such all the extra water in the molecule adds to the weight, same can be said for the sulphate of magnesium.

Targeting 8ppm via Magnesium Sulphate will provide an abundance of Sulphate for the plants.

:)
 

MichaelJ

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Thread starter
Joined
9 Feb 2021
Messages
1,690
Location
Minnesota, USA
2:1 Ca:Mg ratio is unnecessary as plant tissue when analysed by fire assay only yields a ratio of 3:1 Calcium to Magnesium. The solubility of Magnesium to Calcium is 10:1 so it gets transported through river systems quickly and accumulates in the ocean as an opposite ratio of 1:3 Ca:Mg. So the Ratio you should aim for is between 10:1 and 3:1, going for a higher ratio results in no extra benefit for the extra increase in conductivity and hardness.
Hi @X3NiTH , So what your saying is that I should up the Calcium Chloride amount a bit, and lower the Mg Nitrate... How will I then be able to reach my goal of 30 ppm of Nitrate? I guess I could aim for 20 ppm instead (I am not set on a specific ppm as long as its comfortably high for the plant mass) and cut the Mg Nitrate to 8 grams + 1 gram of Mg Sulfate and increate the Ca Chloride to 5 grams which should put me around 3:1. I still want to keep my GH at ~5.5...

The reason why the Magnesium Nitrate weight looks excessive is that it’s a heptahydrate and as such all the extra water in the molecule adds to the weight, same can be said for the sulphate of magnesium.
Thanks for that clarification!
Targeting 8ppm via Magnesium Sulphate will provide an abundance of Sulphate for the plants.
Sounds good.
 
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