How should I use magnesium supplement?

[jnbrex]

Based on my understanding, magnesium isn't consumed like alkalinity and calcium are when corals use them to form calcium carbonate. Without adding any supplemental magnesium, mine is testing at 1350, almost exactly the amount that it should be based on the 1360 - 1420 mg/l advertised on Red Sea Coral Pro Salt Mix.

When you buy the 2-Part Pharma Calcium & Alkalinity Starter Package from BRS, it includes a large amount of magnesium supplement. Why? Am I supposed to be regularly dosing this, or is it just meant to help maintain levels like alk and cal? But why would such a large amount be necessary for maintaining levels, if magnesium isn't used for coral growth like alkalinity and calcium are?

Would it be beneficial to maintain magnesium levels higher than 1360-1420 mg/l, and so it would be necessary to add supplemental magnesium with each water change?

 

[KrisReef]

The product is sold by weight and magnesium is relatively inexpensive?

Check this out:


This one!

I'm trying to say stay focused on CA & Alk. test for Mag now and again and imo it might drop low in 6 months to a year in a heavy growth system, but with water changes you may not need any additions, as Per RMM findings.

 

[Randy Holmes-Farley]

Based on my understanding, magnesium isn't consumed like alkalinity and calcium are when corals use them to form calcium carbonate. Without adding any supplemental magnesium, mine is testing at 1350, almost exactly the amount that it should be based on the 1360 - 1420 mg/l advertised on Red Sea Coral Pro Salt Mix.

When you buy the 2-Part Pharma Calcium & Alkalinity Starter Package from BRS, it includes a large amount of magnesium supplement. Why? Am I supposed to be regularly dosing this, or is it just meant to help maintain levels like alk and cal? But why would such a large amount be necessary for maintaining levels, if magnesium isn't used for coral growth like alkalinity and calcium are?

Would it be beneficial to maintain magnesium levels higher than 1360-1420 mg/l, and so it would be necessary to add supplemental magnesium with each water change?

I devised that recipe and my recommendation is to use it (or a related recipe) as described.

Corals and coralline algae do incorporate magnesium into their skeletons in place of some of the calcium. However, the amount is never more than about 1/10th of the calcium consumption, and often is lower. The two part recipe accounts for this.

With a two part you also need to add magnesium of another important reason that is peculiar to two parts, and both of these reasons need a significant amount. This is a sentence from the article linked below:

In my DIY recipe, I do both for magnesium, with about 1/3 of the magnesium added to offset consumption and 2/3 used to offset the salinity rise issues. That same question can apply to trace elements as well, since they are also rapidly consumed in some cases.

I think you will find this article useful to understand what is going on with this recipe, nd the magnesium third part is specifically addressed in the sections titled sodium and chloride accumulation, ion balance, and What about Ion Consumption Other than Calcium and Carbonate?

How a Two Part Alkalinity and Calcium System Works, and Why it Matters

How a Two Part Alkalinity and Calcium System Works, and Why it Matters By Randy Holmes-Farley This article is intended to help aquarists understand some of the important differences between the great variety of two and three part alkalinity and...

www.reef2reef.com

 

[jnbrex]

I devised that recipe and my recommendation is to use it (or a related recipe) as described.

Corals and coralline algae do incorporate magnesium into their skeletons in place of some of the calcium. However, the amount is never more than about 1/10th of the calcium consumption, and often is lower. The two part recipe accounts for this.

With a two part you also need to add magnesium of another important reason that is peculiar to two parts, and both of these reasons need a significant amount. This is a sentence from the article linked below:

In my DIY recipe, I do both for magnesium, with about 1/3 of the magnesium added to offset consumption and 2/3 used to offset the salinity rise issues. That same question can apply to trace elements as well, since they are also rapidly consumed in some cases.

I think you will find this article useful to understand what is going on with this recipe, nd the magnesium third part is specifically addressed in the sections titled sodium and chloride accumulation, ion balance, and What about Ion Consumption Other than Calcium and Carbonate?

How a Two Part Alkalinity and Calcium System Works, and Why it Matters

How a Two Part Alkalinity and Calcium System Works, and Why it Matters By Randy Holmes-Farley This article is intended to help aquarists understand some of the important differences between the great variety of two and three part alkalinity and...

www.reef2reef.com

Thank you Randy! I think I understand that it’s necessary to dose magnesium for two reasons:

1. The dilution of magnesium (and all other elements) as you replace saltwater with freshwater to counteract the salinity increase of the alk and cal supplements.
2. Biological usage where corals incorporate magnesium into their skeleton in place of calcium.

I’m curious why in the RMM post you recommend dosing 5-10% as much magnesium as calcium, but in the An Improved Do-it-Yourself Two-Part
Calcium and Alkalinity Supplement System article, you write, “Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this [magnesium] stock solution.” Since one gallon is 3785 ml, and 610 ml / 3785 ml = 0.16, according to the article you should dose 16% as much magnesium as calcium or alkalinity supplement.

Why the disparity? I’m sure the chemistry hasn’t changed, so what’s the difference? Or is the BRS recipe somehow different from Recipe #1 (with 3A) from your article?

 

[Randy Holmes-Farley]

When you use a two part, there is a special need for magnesium and sulfate (and other ions) that does not exist with any other method (#1 above). If you use Balling part C for the third part, that accounts for just #1.

The RMM directions does not assume anything about the method and so does not assume you need #1. That’s why the basic RMM amount (only #2) is smaller.

 

[jnbrex]

When you use a two part, there is a special need for magnesium and sulfate (and other ions) that does not exist with any other method (#1 above). If you use Balling part C for the third part, that accounts for just #1.

The RMM directions does not assume anything about the method and so does not assume you need #1. That’s why the basic RMM amount (only #2) is smaller.

Thank you for the explanation! I think I understand now. A 3rd part that contains more than just magnesium and sulfate would be necessary, since all elements would be diluted equally over time.

Would you recommend dosing something like the Korallen-Zucht Coral System alongside the BRS Magnesium Chloride + Magnesium Sulfate supplement to ensure that trace elements aren’t depleted? I’m unclear on how much Coral System to use. They say 1 ml per 5 gallons per week, but that seems totally arbitrary to me since it would depend on how much dilution is occurring, and thus how much two part you’re using.

It seems like using a product like Balling Part C might make more sense, since the trace elements would be in balance with magnesium and sulfate. Balling part C is interesting. I’m surprised that it contains calcium and alkalinity given that it’s meant to be used with two part. How could I calculate the appropriate ratio between alk / cal supplement usage and balling part C?

 

[Randy Holmes-Farley]

Thank you for the explanation! I think I understand now. A 3rd part that contains more than just magnesium and sulfate would be necessary, since all elements would be diluted equally over time.

Would you recommend dosing something like the Korallen-Zucht Coral System alongside the BRS Magnesium Chloride + Magnesium Sulfate supplement to ensure that trace elements aren’t depleted? I’m unclear on how much Coral System to use. They say 1 ml per 5 gallons per week, but that seems totally arbitrary to me since it would depend on how much dilution is occurring, and thus how much two part you’re using.

It seems like using a product like Balling Part C might make more sense, since the trace elements would be in balance with magnesium and sulfate. Balling part C is interesting. I’m surprised that it contains calcium and alkalinity given that it’s meant to be used with two part. How could I calculate the appropriate ratio between alk / cal supplement usage and balling part C

I give my DIY recommendations here:

Randy Recommended DIY Two Part Recipes

There are a whole lot of different DIY recipes around now, and I thought I lay out the differences and my recommendations. In all cases, food grade, USP (pharma) grade, or Analytical Reagent/ACS grades are all good choices for materials. Lower or ungraded materials may be fine, but its more...

www.reef2reef.com

My top picks from that thread are:

A. Baking soda for alk part, calcium chloride for calcium part, and Balling Part 3 to balance all other ions. This is a low pH recipe. it is my DIY #2 with a changed part 3.

B. Baked baking soda (washing soda, sodium carbonate) for alk part, calcium chloride for calcium part, and Balling Part 3 to balance all other ions. This is a high pH two party, and can be twice as potent as A. It is my DIY #1 with a changed part 3.

C. Sodium hydroxide for alk part, calcium chloride for calcium part, and Balling Part 3 to balance all other ions. This is the highest pH alk part possible, and can be made higher in potency than the others (if required).

Then one potentially needs to add magnesium and assorted trace elements to offset consumption. Normal commercial or DIY versions of those additives should be fine, and I recommend RMM for the magnesium: adding it not based on testing, but in relation to calcium consumption.

 

[Randy Holmes-Farley]

Thank you for the explanation! I think I understand now. A 3rd part that contains more than just magnesium and sulfate would be necessary, since all elements would be diluted equally over time.

Would you recommend dosing something like the Korallen-Zucht Coral System alongside the BRS Magnesium Chloride + Magnesium Sulfate supplement to ensure that trace elements aren’t depleted? I’m unclear on how much Coral System to use. They say 1 ml per 5 gallons per week, but that seems totally arbitrary to me since it would depend on how much dilution is occurring, and thus how much two part you’re using.

It seems like using a product like Balling Part C might make more sense, since the trace elements would be in balance with magnesium and sulfate. Balling part C is interesting. I’m surprised that it contains calcium and alkalinity given that it’s meant to be used with two part. How could I calculate the appropriate ratio between alk / cal supplement usage and balling part C?

I am not certain that Balling part C contains alk and/or calcium (it does by the description, but am not 100% certain it does), but ignore it as it won't be problematic.