DIY Magnesium

Gungo · Aug 23, 2022

Hello,

I'm trying to figure out the correct amount to make the DIY magnesium supplement. I find all the measurements in cups, but I need them in grams. For example, the randy's recipe is 5 cups of magnesium chloride and 3 cups of magnesium sulfate. Can someone give me the correct relation between 1 cup to grams when talking about magnesium powder?

Thanks

GMay · Aug 23, 2022

frcarvajal said:
Hello,

I'm trying to figure out the correct amount to make the DIY magnesium supplement. I find all the measurements in cups, but I need them in grams. For example, the randy's recipe is 5 cups of magnesium chloride and 3 cups of magnesium sulfate. Can someone give me the correct relation between 1 cup to grams when talking about magnesium powder?

Thanks

I've converted the two-part recipes into metric weights and volumes. I've attached it.

Randy Holmes-Farley · Aug 23, 2022

frcarvajal said:
Hello,

I'm trying to figure out the correct amount to make the DIY magnesium supplement. I find all the measurements in cups, but I need them in grams. For example, the randy's recipe is 5 cups of magnesium chloride and 3 cups of magnesium sulfate. Can someone give me the correct relation between 1 cup to grams when talking about magnesium powder?

Thanks

Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

To perfect such a recipe, it's imperative to know the amounts of sulfate in Epsom salts (39%), the amount of chloride in magnesium chloride hexahydrate (34.9%), and their bulk densities, because most aquarists will use a volume based measurement (1.05 g/cm3 for Epsom salts and 0.85 g/cm3 for magnesium chloride hexahydrate solids). Taking all these factors into account, the desired volume ratio is 10:1, MAG flake to Epsom salts, as a supplement; for instance, 10 cups MAG flake and 1 cup Epsom salts.

GMay · Aug 23, 2022

Randy Holmes-Farley said:
Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

To perfect such a recipe, it's imperative to know the amounts of sulfate in Epsom salts (39%), the amount of chloride in magnesium chloride hexahydrate (34.9%), and their bulk densities, because most aquarists will use a volume based measurement (1.05 g/cm3 for Epsom salts and 0.85 g/cm3 for magnesium chloride hexahydrate solids). Taking all these factors into account, the desired volume ratio is 10:1, MAG flake to Epsom salts, as a supplement; for instance, 10 cups MAG flake and 1 cup Epsom salts.

Suggested corrections are always welcome.

Randy Holmes-Farley · Aug 23, 2022

GMay said:
Suggested corrections are always welcome.

Bulk densities will vary by brand.

GMay · Aug 23, 2022

Using the densities provided that would be:
MgSO4 158.7 gr/L
MgCl2 223.7 gr/L

Gungo · Aug 23, 2022

Now i'm kinda confused. You say that the perfect ratio is 10:1 but also the recipe is 5 chloride to 3 sulfate. BRS also has different ratios. Why is that?

Randy Holmes-Farley · Aug 23, 2022

frcarvajal said:
Now i'm kinda confused. You say that the perfect ratio is 10:1 but also the recipe is 5 chloride to 3 sulfate. BRS also has different ratios. Why is that?

Because I devised different recipes for different purposes. The 10:1 is the stand along magnesium additive to use when not using calcium chloride. The 5:3 is oart 3 of the 2/3 part recipe.

I explain that in the article:
Note also that this recipe (#3) is different from that given in my DIY two-part recipe, because in that case more magnesium sulfate is necessary to offset the rise in chloride that is provided by both the calcium chloride and the magnesium chloride.

Gungo · Aug 23, 2022

Just to confirm that we are on the same page, if I'm using your recipe of 594 grams of soda ash and 500g of calcium chloride as two parts. What's the best/recommended recipe for magnesium?

Randy Holmes-Farley · Aug 24, 2022

frcarvajal said:
Just to confirm that we are on the same page, if I'm using your recipe of 594 grams of soda ash and 500g of calcium chloride as two parts. What's the best/recommended recipe for magnesium?

5:3, dosed in amounts dosed of the other two parts as recommended in the two part article, not based on magnesium testing (unless magnesium is already well above your target).

Gungo · Aug 24, 2022

Perfect, thanks! And to correct the magnesium levels, lets say if I am in 1,100 and I want to go to 1,350 which solution works best?

Randy Holmes-Farley · Aug 24, 2022

frcarvajal said:
Perfect, thanks! And to correct the magnesium levels, lets say if I am in 1,100 and I want to go to 1,350 which solution works best?

10:1. That will leave the chloride/sulfate ratio where it should be.

Gungo · Dec 29, 2022

Hello Randy, was trying to get in the webpage and it isn't working.

Randy Holmes-Farley · Dec 29, 2022

The web site appears to be down at the moment, but here's an archived version. If a site doesn't work, it's always worth a try to put the link into the wayback machine site:

http://web.archive.org/web/20170328124558/http://reefkeeping.com/issues/2006-07/rhf/index.php

http://web.archive.org/web/20160314075436/http://reefkeeping.com/issues/2006-02/rhf/index.php

KyleC · Sep 8, 2024

Can anyone help? I have epsom salts and magnesium flakes. I'm in the UK. I know the ratio I need to use is 10:1 flakes:epsom, but how much is that in grams when using 1 litre of RODI water?