Should I dose for magnesium?

[stanleo]

Need some advice. Tank is two years old running well. I have an auto doser that doses BRS soda ash and BRS calcium chloride. For months this kept them stable
at 9 Alk and 450 calcium. My magnesium has always tested high at 1520 or 1480 since I started the tank. Now over the last weeks this has changed. Every week I now test 7.8 alk. Everytime I dose back up to 9. I increased the dosing from to 40 ml daily to 50 ml daily last week and again today it tested at 7.8. I Dosed it back up to 9 and now I upped the dosing to 70 ml and upped the dosing for calcium from 30 ml daily to 42 ml daily. I have checked the doser and it is calibrated and doses at the right times. 5 times a day for alk and 6 times a day for calcium. I assume this change in alk and calcium has something to do with the drop in magnesium. Should I start dosing magnesium? What is the best product to use for this?

This is my spread sheet for keeping track of my test results and I have four months worth of data that I can post if that will help. I have no idea why the rise in calcium for Jan 6 through Jan 20 but after that it started steadily dropping.

 

[HuduVudu]

Your test might be bad.

 

[LRT]

Following.
What are you growing in system?

 

[stanleo]

Following.
What are you growing in system?

Monti, hammer, birdsnest, lobo, GSP, kenya tree, xenias, brain coral. And coraline algae lol.

 

[stanleo]

Your test might be bad.

That thought had occurred to me, I have refills for the tests coming. But once I dosed alk back to nine, I test again and it shows 9.

 

[Randy Holmes-Farley]

The DIY two part that I designed (that BRS uses) is intended to dose the magnesium part without need to be testing it. Other two parts, Balling and CaCO3/CO2 reactors do this out of sight. Just because you can see it doesn't mean you should mess with the recipe. lol

I'd recommend dosing the recommended amount: 610 ml of the magnesium part over the course of adding 1 gallon of the alk or calcium part. Or 1 ml of the magneisum part for each 6 mL of the alk or calcium part.

It is certainly Ok to not dose magnesium if for some reason it is already too high, and to make corrective doses if it is clearly to low.

But magnesium testing is way too insensitive to constantly be jiggering the dosing.

FWIW, the Red Sea magnesium kits gives folks lots of challenges and seems, IMO, to often give folks higher values than other kits.

 

[stanleo]

The DIY two part that I designed (that BRS uses) is intended to dose the magnesium part without need to be testing it. Other two parts, Balling and CaCO3/CO2 reactors do this out of sight. Just because you can see it doesn't mean you should mess with the recipe. lol

I'd recommend dosing the recommended amount: 610 ml of the magnesium part over the course of adding 1 gallon of the alk or calcium part. Or 1 ml of the magneisum part for each 6 mL of the alk or calcium part.

It is certainly Ok to not dose magnesium if for some reason it is already too high, and to make corrective doses if it is clearly to low.

But magnesium testing is way too insensitive to constantly be jiggering the dosing.

FWIW, the Red Sea magnesium kits gives folks lots of challenges and seems, IMO, to often give folks higher values than other kits.

So what product should I be using?

 

[Randy Holmes-Farley]

If you are using My DIY recipe 1 (in the article below, sold by BRS) then you should use the magnesium recipe #1, part 3. BRS sells the ingredients if you do not have it already:

Pharma Magnesium Mix for 2-Part Maintenance

Ultra Pure Magnesium Additive for 2-Part Maintenance in your Reef Tank! Maintaining proper magnesium levels helps achieve the essential balance of calcium and alkalinity in your tank by preventing excess calcium carbonate precipitation. Not all magnesium additives are created equal and the...

www.bulkreefsupply.com

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

Recipe #1, Part 3: The Magnesium Portion

The magnesium portion gives us two options, with Part 3A being preferred from an aquarium chemistry standpoint. Pick one and follow the same dosing directions regardless of which version you select.

Recipe #1, Part 3A

Dissolve Epsom salts (3 cups) and magnesium chloride hexahydrate sold by the Dead Sea Works company (5 cups) in enough purified freshwater to make 1 gallon total volume. There will likely be a precipitate that forms even if you fully dissolve both ingredients separately. That precipitate is calcium sulfate (calcium as an impurity in the magnesium chloride and sulfate from the Epsom salts). It is fine and appropriate to dose the precipitate along with the remainder of the fluid by shaking it up before dosing.

This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. You can add it all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium, 70,000 ppm sulfate and 86,000 ppm chloride.

Recipe #1, Part 3B

Dissolve a 64-ounce container of Epsom salts (about 8 cups) in enough purified freshwater to make 1 gallon total volume. This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. It can be added all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium and 187,000 ppm sulfate.

 

[stanleo]

If you are using My DIY recipe 1 (in the article below, sold by BRS) then you should use the magnesium recipe #1, part 3. BRS sells the ingredients if you do not have it already:

Pharma Magnesium Mix for 2-Part Maintenance

Ultra Pure Magnesium Additive for 2-Part Maintenance in your Reef Tank! Maintaining proper magnesium levels helps achieve the essential balance of calcium and alkalinity in your tank by preventing excess calcium carbonate precipitation. Not all magnesium additives are created equal and the...

www.bulkreefsupply.com

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

Recipe #1, Part 3: The Magnesium Portion

The magnesium portion gives us two options, with Part 3A being preferred from an aquarium chemistry standpoint. Pick one and follow the same dosing directions regardless of which version you select.

Recipe #1, Part 3A

Dissolve Epsom salts (3 cups) and magnesium chloride hexahydrate sold by the Dead Sea Works company (5 cups) in enough purified freshwater to make 1 gallon total volume. There will likely be a precipitate that forms even if you fully dissolve both ingredients separately. That precipitate is calcium sulfate (calcium as an impurity in the magnesium chloride and sulfate from the Epsom salts). It is fine and appropriate to dose the precipitate along with the remainder of the fluid by shaking it up before dosing.

This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. You can add it all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium, 70,000 ppm sulfate and 86,000 ppm chloride.

Recipe #1, Part 3B

Dissolve a 64-ounce container of Epsom salts (about 8 cups) in enough purified freshwater to make 1 gallon total volume. This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. It can be added all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium and 187,000 ppm sulfate.

That is exactly what I was looking for. Thank you so much.

 

[stanleo]

If you are using My DIY recipe 1 (in the article below, sold by BRS) then you should use the magnesium recipe #1, part 3. BRS sells the ingredients if you do not have it already:

Pharma Magnesium Mix for 2-Part Maintenance

Ultra Pure Magnesium Additive for 2-Part Maintenance in your Reef Tank! Maintaining proper magnesium levels helps achieve the essential balance of calcium and alkalinity in your tank by preventing excess calcium carbonate precipitation. Not all magnesium additives are created equal and the...

www.bulkreefsupply.com

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

Recipe #1, Part 3: The Magnesium Portion

The magnesium portion gives us two options, with Part 3A being preferred from an aquarium chemistry standpoint. Pick one and follow the same dosing directions regardless of which version you select.

Recipe #1, Part 3A

Dissolve Epsom salts (3 cups) and magnesium chloride hexahydrate sold by the Dead Sea Works company (5 cups) in enough purified freshwater to make 1 gallon total volume. There will likely be a precipitate that forms even if you fully dissolve both ingredients separately. That precipitate is calcium sulfate (calcium as an impurity in the magnesium chloride and sulfate from the Epsom salts). It is fine and appropriate to dose the precipitate along with the remainder of the fluid by shaking it up before dosing.

This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. You can add it all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium, 70,000 ppm sulfate and 86,000 ppm chloride.

Recipe #1, Part 3B

Dissolve a 64-ounce container of Epsom salts (about 8 cups) in enough purified freshwater to make 1 gallon total volume. This solution is added much less frequently than the other two parts. Each time you finish adding a gallon of both parts of Recipe #1, add 610 mL (2 ½ cups) of this stock solution. It can be added all at once or over time as you choose, depending on the aquarium's size and set up. Add it to a high flow area, preferably a sump. In a very small aquarium, or one without a sump, I suggest adding it slowly.

The first time it's added, I recommend adding just a small portion and making sure there isn't any problem (such as corals closing up due to stress) before adding the remainder. Make sure corals and other organisms don't get blasted with locally high concentrations of the main ingredients or impurities, or else they may become stressed. This solution contains about 47,000 ppm magnesium and 187,000 ppm sulfate.

I want to make sure I am doing this right. Today I tested and my magnesium dropped again this time to 1280. I got this magnesium mix from BRS

Pharma Magnesium Mix for General Adjustments

Ultra Pure Magnesium Additive for General Adjustments in your Reef Tank! Maintaining proper magnesium levels helps achieve the essential balance of calcium and alkalinity in your tank by preventing excess calcium carbonate precipitation. Not all magnesium additives are created equal and the...

www.bulkreefsupply.com

I did the calculator and for a 140 gallon system to go from 1280 mag to 1360 takes 903 ml of the magnesium solution. Does that sound right and safe? It says to limit changes to no more than 100ppm daily.

Aquarium and Reef Calculators - Bulk Reef Supply

Bulk Reef Supply - Saltwater Aquarium Supplies for Reef Tanks

www.bulkreefsupply.com

Going forward to keep it sable, since I dose 60 ml daily of calcium and alkalinity, should I dose 10 ml daily of magnesium? That's how I understood it.

 

[Randy Holmes-Farley]

There's no chance the magnesium dropped 200 ppm in a month. I suspect there are testing issues involved.

It may be 1280 ppm now (which is fine). All your numbers are fine for it.

You are only consuming/adding 7 ppm of calcium per day with that 60 mL, so the actual demand for magnesium is less than 1 ppm per day.

Yes, the 10 mL a day is appropriate, which adds less than 1 ppm per day.

 

[stanleo]

There's no chance the magnesium dropped 200 ppm in a month. I suspect there are testing issues involved.

It may be 1280 ppm now (which is fine). All your numbers are fine for it.

You are only consuming/adding 7 ppm of calcium per day with that 60 mL, so the actual demand for magnesium is less than 1 ppm per day.

Yes, the 10 mL a day is appropriate, which adds less than 1 ppm per day.

Thank you. You have been a big help.

 

[s0mthinG]

There's no chance the magnesium dropped 200 ppm in a month. I suspect there are testing issues involved.

It may be 1280 ppm now (which is fine). All your numbers are fine for it.

You are only consuming/adding 7 ppm of calcium per day with that 60 mL, so the actual demand for magnesium is less than 1 ppm per day.

Yes, the 10 mL a day is appropriate, which adds less than 1 ppm per day.

I'm just curious because I've read (but not exactly understood) about reaching a point in some concentrations of either calcium or alkalinity that causes I can't remember if it was magnesium or either alk or calcium to drop dramatically to a saturation point. Could you explain this concept to me?

 

[Randy Holmes-Farley]

I'm just curious because I've read (but not exactly understood) about reaching a point in some concentrations of either calcium or alkalinity that causes I can't remember if it was magnesium or either alk or calcium to drop dramatically to a saturation point. Could you explain this concept to me?

Sure, but it is not exactly a tipping point.

This article covers the idea in great detail. If anything is not clear, I'm happy to try to explain it further.

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com

This is one of the summary sections that might give a quickie answer to your main questions:

Summary of Abiotic Calcium Carbonate Solubility Effects
This section summarizes many of the ideas covered in the above sections and puts them together to form a more complete understanding.

1. Normal seawater (calcium = 420 ppm, pH = 8.2, alkalinity = 2.5 meq/L (7 dKH)) is significantly supersaturated with calcium carbonate. That is, more of the ions (several-fold more, actually) are already in solution than would be stable in the long term. The rate at which calcium and carbonate ions land on a pure calcium carbonate surface in seawater is higher than the rate at which they leave that surface. This supersaturation sets up the potential for calcium carbonate precipitation.

2. The potential precipitation described in (1) above is "delayed," sometimes indefinitely, as magnesium gets onto the growing calcium carbonate crystal structure. The magnesium alters the surface, making it no longer look like calcium carbonate. This "poisoning" of the surface slows or stops the precipitation of additional calcium and carbonate onto it. Abnormally low levels of magnesium will be less effective at preventing the precipitation of calcium carbonate.

3. The more calcium and carbonate there is in excess of "saturation," the faster the potential rate of calcium carbonate's precipitation. In other words, the more the "on rate" exceeds the "off rate," the faster precipitation can take place. If the potential for rapid precipitation exists due to a very high supersaturation condition, the more likely such precipitation is to overwhelm magnesium's ability to prevent it.

4. The factors that lead to higher supersaturation are higher calcium, alkalinity and pH. The effect of pH is especially dramatic, with an increase of 0.3 pH units being equivalent to a doubling of calcium or alkalinity in terms of the supersaturation (or in terms of the driving force for precipitation). This pH effect is why an overdose of limewater can cause calcium carbonate precipitation, and why dosing limewater into a skimmer or other enclosed system (such as a pump intake) can increase precipitation of calcium carbonate inside it. It is also why reducing the water's pH in a calcium carbonate/carbon dioxide reactor can dissolve calcium carbonate media.

5. If the water is below "saturation" with respect to calcium and carbonate, then no net precipitation will take place. Under normal seawater conditions, where the water is, in fact, supersaturated with calcium carbonate, there is still little precipitation, largely because of the magnesium in the seawater. Consequently, if calcium or alkalinity is lower than "normal" in a reef aquarium, then boosting either (or both) calcium and alkalinity to natural levels will cause no rapid precipitation of calcium carbonate. In other words, boosting one under these conditions will not cause a rapid decline in the other.

6. When calcium carbonate precipitates, it uses up a fixed ratio of calcium and carbonate (1:1, or about 20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity). This ratio is the same as corals use to deposit their calcium carbonate skeletons. Abiotic precipitation of calcium carbonate, like coral skeletal formation, can incorporate other ions, such as magnesium and strontium. That incorporation will reduce the above ratio from 20 ppm calcium for each 1 meq/L of alkalinity to a slightly lower value. Over the long term this process can deplete magnesium and strontium in an aquarium if only calcium and alkalinity are supplemented.

 

[Randy Holmes-Farley]

I would add that both organics and phosphate play a similar role to magnesium is reducing or preventing abiotic precipitation of calcium carbonate, but they get much less discussion in that context.

Still, their absence is why, IMO, artificial seawater mixes with a high alk (e.g., Red Sea Coral Pro) are so prone to calcium carbonate precipitation, when an aquarium with the same alk and calcium and magnesium levels is not.

 

[s0mthinG]

Sure, but it is not exactly a tipping point.

This article covers the idea in great detail. If anything is not clear, I'm happy to try to explain it further.

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com

This is one of the summary sections that might give a quickie answer to your main questions:

Summary of Abiotic Calcium Carbonate Solubility Effects
This section summarizes many of the ideas covered in the above sections and puts them together to form a more complete understanding.

1. Normal seawater (calcium = 420 ppm, pH = 8.2, alkalinity = 2.5 meq/L (7 dKH)) is significantly supersaturated with calcium carbonate. That is, more of the ions (several-fold more, actually) are already in solution than would be stable in the long term. The rate at which calcium and carbonate ions land on a pure calcium carbonate surface in seawater is higher than the rate at which they leave that surface. This supersaturation sets up the potential for calcium carbonate precipitation.

2. The potential precipitation described in (1) above is "delayed," sometimes indefinitely, as magnesium gets onto the growing calcium carbonate crystal structure. The magnesium alters the surface, making it no longer look like calcium carbonate. This "poisoning" of the surface slows or stops the precipitation of additional calcium and carbonate onto it. Abnormally low levels of magnesium will be less effective at preventing the precipitation of calcium carbonate.

3. The more calcium and carbonate there is in excess of "saturation," the faster the potential rate of calcium carbonate's precipitation. In other words, the more the "on rate" exceeds the "off rate," the faster precipitation can take place. If the potential for rapid precipitation exists due to a very high supersaturation condition, the more likely such precipitation is to overwhelm magnesium's ability to prevent it.

4. The factors that lead to higher supersaturation are higher calcium, alkalinity and pH. The effect of pH is especially dramatic, with an increase of 0.3 pH units being equivalent to a doubling of calcium or alkalinity in terms of the supersaturation (or in terms of the driving force for precipitation). This pH effect is why an overdose of limewater can cause calcium carbonate precipitation, and why dosing limewater into a skimmer or other enclosed system (such as a pump intake) can increase precipitation of calcium carbonate inside it. It is also why reducing the water's pH in a calcium carbonate/carbon dioxide reactor can dissolve calcium carbonate media.

5. If the water is below "saturation" with respect to calcium and carbonate, then no net precipitation will take place. Under normal seawater conditions, where the water is, in fact, supersaturated with calcium carbonate, there is still little precipitation, largely because of the magnesium in the seawater. Consequently, if calcium or alkalinity is lower than "normal" in a reef aquarium, then boosting either (or both) calcium and alkalinity to natural levels will cause no rapid precipitation of calcium carbonate. In other words, boosting one under these conditions will not cause a rapid decline in the other.

6. When calcium carbonate precipitates, it uses up a fixed ratio of calcium and carbonate (1:1, or about 20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity). This ratio is the same as corals use to deposit their calcium carbonate skeletons. Abiotic precipitation of calcium carbonate, like coral skeletal formation, can incorporate other ions, such as magnesium and strontium. That incorporation will reduce the above ratio from 20 ppm calcium for each 1 meq/L of alkalinity to a slightly lower value. Over the long term this process can deplete magnesium and strontium in an aquarium if only calcium and alkalinity are supplemented.

Fantastic! So let me see if I get this right, The main thing that would cause rapid precipitation of this super saturated carbonate solution is abnormally low levels of magnesium? I understand the other factors such as pH and calcium / alkalinity do play a role, but magnesium acts almost as a disguise for the actual amounts of carbonate in the water allowing it to harbor more than a normal non-saturated solution?

 

[Randy Holmes-Farley]

Fantastic! So let me see if I get this right, The main thing that would cause rapid precipitation of this super saturated carbonate solution is abnormally low levels of magnesium? I understand the other factors such as pH and calcium / alkalinity do play a role, but magnesium acts almost as a disguise for the actual amounts of carbonate in the water allowing it to harbor more than a normal non-saturated solution?

I would not say that magnesium at low levels is any more responsible than is high pH or alkalinity. It not an easy thing to quantify, but I'll, note that Red Sea Coral Pro, with high alk, is very prone to precipitation, despite having plenty of magnesium.

IMO, folks blame magnesium for more than its due, and tend to neglect the pH as a major driver of precipitation.