What is the Correct DIY Magnesium Solution

[redfishblewfish]

I am a Dr. Randy DIY two part user (with his MAG solution as well; Recipe 1, part 3A). I just listened to a podcast that included Dr. Craig Bingman. If I understood correctly, he stated a balanced magnesium solution would be a mix of 10 volumes of magnesium chloride hexahydrate with 1 volume of Epsom salts. Dr. Holmes-Farley says a mix of 5 cups magnesium chloride hexahydrate with 3 cups of Epsom salts gives you the "correct" ionic balance.

What am I missing? These two recipes look to be considerably different.

 

[bertoni]

The 10:1 ratio is correct for use on its own. The 5:3 ratio is appropriate when you're dosing the DIY 2-part. This article goes into the math:

http://reefkeeping.com/issues/2006-02/rhf/index.php#21

 

[redfishblewfish]

Jonathan, thanks for replying. Just to make sure my little pea-brain understands, what you are saying is that if I was using something other then two part (lets say kalkwasser of a calcium reactor), I would want to use Dr. Bingman's recipe over Dr. Holmes Farley's recipe to maintain proper ionic balance. Is that correct?

 

[disc1]

That is correct. The 3:5 ratio is to account for the extra chloride coming from the two part calcium part.

 

[DiscusHeckel]

How many grams is 1 US cup please? I looked at the internet, I can get liquid conversion of 1 US cup of water to grams.

More specifically, based on Randy's recipe 2, how many grams of MgCl2 is equal to per 1 US cup of MgCl2? My head hurts if a measurement is not based on metrics.

Many thanks

 

[disc1]

How many grams is 1 US cup please? I looked at the internet, I can get liquid conversion of 1 US cup of water to grams.

More specifically, based on Randy's recipe 2, how many grams of MgCl2 is equal to per 1 US cup of MgCl2? My head hurts if a measurement is not based on metrics.

Many thanks

Unfortunately you need to know the density to do that conversion. 1 cup of gold weighs a whole lot more than 1 cup of aerogel. Maybe someone has done the measurement before and can give an approximate weight.

But beware, hydration state counts. So 1 cup of hexahydrate is a lot less magnesium than 1 cup of anhydrous. You'll need to be very specific about what you are measuring.

 

[DiscusHeckel]

Unfortunately you need to know the density to do that conversion. 1 cup of gold weighs a whole lot more than 1 cup of aerogel. Maybe someone has done the measurement before and can give an approximate weight.

But beware, hydration state counts. So 1 cup of hexahydrate is a lot less magnesium than 1 cup of anhydrous. You'll need to be very specific about what you are measuring.

Thanks David. I have magnesium chloride hexahydrate (in flake form) and magnesium sulfate heptahydrate.

It sounds as if the best way forward for me is to use a measuring jug. However, measuring jugs in the UK are based on UK cupas opposed to US cup. Arrgh...

 

[Randy Holmes-Farley]

Any volumes with the same ratio will be fine. You can use the UK cups.

 

[redfishblewfish]

Not to mention the difference between a UK cup versus a US cup is 284 mls versus 237 mls, respectively. Either measure using mls or use approximately 13/16 of a UK cup per US cup to make the "US" dilution of Magnesium solution.


EDIT TO ADD: Darn I'm slow......if you simply use UK cups (5:3) for the ingredients and bring that up to a UK gallon with RO/DI water, you have the exact concentration of the stuff quoted in Randy's recipe article.....Done!

 

[disc1]

Thanks David. I have magnesium chloride hexahydrate (in flake form) and magnesium sulfate heptahydrate.

It sounds as if the best way forward for me is to use a measuring jug. However, measuring jugs in the UK are based on UK cupas opposed to US cup. Arrgh...

Any volumes with the same ratio will be fine. You can use the UK cups.

The only issue is knowing then how much water to dissolve in so you can use the handy dandy calculator to get the dosage.

 

[DiscusHeckel]

Any volumes with the same ratio will be fine. You can use the UK cups.

Too right. It is 23.46 here in the UK. It has been a long day. Thank you.

The only issue is knowing then how much water to dissolve in so you can use the handy dandy calculator to get the dosage.

I US gallon is 3.79 litres. For the sake of my mental sanity, I will prepare solution totalling up to 3.79 litres. Otherwise, we are talking about 3/3.79 (i.e. 0.8 US cups per litre, etc).

I will be using this calculator to adjust my magnesium levels once I have the solution.

Although I have been using Randy's recipe 2 since I started reef keeping almost six years ago, I always topped up magnesium using 1:7 ratio using a different calculator. For a while, I only used magnesium chloride, but struggled with keeping the salinity stable.

By switching to 3:5 ratio, what visible changes should I expect to see in my tank?

 

[redfishblewfish]

..........
I US gallon is 3.79 litres. For the sake of my mental sanity, I will prepare solution totalling up to 3.79 litres. Otherwise, we are talking about 3/3.79 (i.e. 0.8 US cups per litre, etc).

........................

Maybe you missed my edit above, but if you simply use all UK measurements you will have the exact concentration and ratio of all ingredients. That is, use UK cups of the two ingredients made up to a UK gallon, and you have the exact recipe of Dr. Randy Holmes Farley.

 

[DiscusHeckel]

Maybe you missed my edit above, but if you simply use all UK measurements you will have the exact concentration and ratio of all ingredients. That is, use UK cups of the two ingredients made up to a UK gallon, and you have the exact recipe of Dr. Randy Holmes Farley.

Yes, I did. I am sorry.

 

[Randy Holmes-Farley]

By switching to 3:5 ratio, what visible changes should I expect to see in my tank?

None, I expect. We do not really know how the ratio of chloride to sulfate impacts reef creatures, but they do not seem very sensitive to it.

 

[DiscusHeckel]

I have just mixed 3 (UK) cups of Mag Sulphate and 5 (UK) cups of Mag Chloride in enough RODI to make 1 (UK) gallon of solution as per the discussion above. The solution looked very milky to begin with, but it appears to have settled now.

I used this calculator to raise the magnesium levels by 30 ppm. After testing my tank water, the magnesium levels have only risen by 15 ppm.

I have been careful in adding the right amounts of magnesium salts. I wonder what I have done wrong (apart from a possible testing error)?

Cheers

 

[Randy Holmes-Farley]

Testing error or calculation error are about all that can go wrong (assuming the products are what you think they are), and 15 ppm testing error in magnesium is not very significant. That's only a 1% error. Few hobby kits are even that accurate.

 

[DiscusHeckel]

Testing error or calculation error are about all that can go wrong (assuming the products are what you think they are), and 15 ppm testing error in magnesium is not very significant. That's only a 1% error. Few hobby kits are even that accurate.

Thanks Randy.

In your DIY article, you state that "Each time you finish adding a gallon of both parts of Recipe #2, add 305 mL (1 ¼ cups) of this stock solution." If I understand your article correctly, by doing that we maintain the correct ionic balance.

I use your Recipe #2. In my case, should I still use 305 ml as per the article or 610 ml in case the products I used are not what I think they are.

Moreover, is it still OK to use this solution on a one-off basis to make corrections, e.g. raising the magnesium levels in fresh salt mix?

Regards

 

[dkeller_nc]

Technically, the magnesium recipes in Randy's article are designed to "make up for" the concentration of chloride relative to sulfate when using a Calcium Chloride/Sodium Carbonate/Bicarbonate 2-part solution.

If one wants to adjust the magnesium level in a prepared salt mix, you'd want to use a proportion of mag chloride to mag sulfate that mimics NSW's ratio of chloride to sulfate (about 7 to 1 by weight).

 

[DiscusHeckel]

Technically, the magnesium recipes in Randy's article are designed to "make up for" the concentration of chloride relative to sulfate when using a Calcium Chloride/Sodium Carbonate/Bicarbonate 2-part solution.

If one wants to adjust the magnesium level in a prepared salt mix, you'd want to use a proportion of mag chloride to mag sulfate that mimics NSW's ratio of chloride to sulfate (about 7 to 1 by weight).

Thanks. If I want to make one-off adjustments to Mg levels in my tank, I need to use NSW's ratio (7:1) too. Correct? This is what I have been doing for many years. As long as I do not make frequent adjustments I should not disturb the ionic balance between sulphates and chlorides, which is what I have ignored all these years despite using Randy's recipe 2 (I guess without the magnesium part).

 

[Randy Holmes-Farley]

The solid volume ratio of magneisum chloride hexahydrate and magneisum sulfate heptahydrate is about 10:1.

Any similar ratio will be fine.

I discuss it here:

Do-It-Yourself Magnesium Supplements for the Reef Aquarium
http://reefkeeping.com/issues/2006-07/rhf/index.php

from it:

Using both Epsom salts and MAG flake, dissolve 7¼ cups MAG flake and ¾ cup Epsom salts in one gallon of water, and use that to supplement magnesium in amounts determined using this linked online calculator, with the entry "Randy's Recipes 1 and 2 Versions A and B," and ignore for this purpose what those designations mean. This recipe is preferred, but its advantage over recipe #2 is minimal in most cases.

Note that combining the two materials in solution can result in some precipitation of calcium sulfate (calcium and sulfate are impurities in the MAG flake and the Epsom salts, respectively. To assure yourself that the two materials have fully dissolved, dissolve each separately in some freshwater before combining them. Some calcium sulfate precipitation is acceptable, and it is okay to let the solids get into the aquarium, assuming you can dose in a way that prevents them from landing on delicate organisms.

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.