Magnesium Levels Don’t Go Down

[JCas06]

Hello,

I have a 72 gallon fairly heavily stocked mixed reef tank. I have noticed that my Magnesium levels never seem to drop. I dose BRS 70 ml of calcium and alkalinity each day through a dosing unit but I never have to add any magnesium. I have been testing calcium, alkalinity, and magnesium regularly for the last 3 months and my mag is always at 1500 on the salifert test kits and just tested with Red Sea and was 1600. I do a larger water change about once a month with coralife salt. Alkalinity is typically around 8 dkh and calcium 410. I did battle a precipitation problem before when I was manually dosing. Since purchasing a dosing unit it has improved a lot but I do still get this grey dust in the tank. I have the unit dose Cal and Alk an hour apart throughout the 24 hour cycle. Why is my tank not using up any magnesium?

Thank you,
Jason

 

[bif24701]

Mag isn’t consumed like Cal and ALK. Adding two part Mag mix chloride/sulfite isn’t just about sustaining Mag levels as it is about maintaining correct ion balance between chloride and sulfite. If you do regular water changes that often is enough to maintain ion and Mag levels.

 

[Randy Holmes-Farley]

Hello,

I have a 72 gallon fairly heavily stocked mixed reef tank. I have noticed that my Magnesium levels never seem to drop. I dose BRS 70 ml of calcium and alkalinity each day through a dosing unit but I never have to add any magnesium. I have been testing calcium, alkalinity, and magnesium regularly for the last 3 months and my mag is always at 1500 on the salifert test kits and just tested with Red Sea and was 1600. I do a larger water change about once a month with coralife salt. Alkalinity is typically around 8 dkh and calcium 410. I did battle a precipitation problem before when I was manually dosing. Since purchasing a dosing unit it has improved a lot but I do still get this grey dust in the tank. I have the unit dose Cal and Alk an hour apart throughout the 24 hour cycle. Why is my tank not using up any magnesium?

Thank you,
Jason

Magnesium consumption is VERY slow, about 1/10th of the calcium rate, so not usually more than 1-2 ppm per day max. If you use a salt mix with excessive magnesium, that will offset apparent usage (which really doesn't mean don't use the magnesium part as designed since that might lead to other issues related to sulfate rather than magnesium).

 

[JCas06]

Magnesium consumption is VERY slow, about 1/10th of the calcium rate, so not usually more than 1-2 ppm per day max. If you use a salt mix with excessive magnesium, that will offset apparent usage (which really doesn't mean don't use the magnesium part as designed since that might lead to other issues related to sulfate rather than magnesium).

Ok I now understand that magnesium is used very slowly and that my salt mix may be enough to keep my levels up without supplementing magnesium. But your saying I should still be using the magnesium part of the part system (which I did also purchase from BRS along with the cal and alk) anyways? And that not dosing the magnesium part could lead to sulfate issues? Can you explain that more please because in my beginner mind I’m thinking supplementing magnesium will just raise my mag levels through the roof.

 

[Randy Holmes-Farley]

Ok I now understand that magnesium is used very slowly and that my salt mix may be enough to keep my levels up without supplementing magnesium. But your saying I should still be using the magnesium part of the part system (which I did also purchase from BRS along with the cal and alk) anyways? And that not dosing the magnesium part could lead to sulfate issues? Can you explain that more please because in my beginner mind I’m thinking supplementing magnesium will just raise my mag levels through the roof.

My DIY two part (which you are using), like most commercial two parts (e.g., B-ionic by ESV) is designed to maintain magnesium where it is, and not to boost it or deplete it. Unfortunately, people see the magnesium with my DIY and don't see it so don't stress out over it when using commercial two parts, CaCO3/CO2 reactors, etc.

Of course, if you do not use the magnesium part, the levels will become lower than if you used it. You are probably depleting magnesium by about 1-2 ppm per day, at which rate it takes a long time to see with a kit.

Assuming the high values are accurate (which they may not be), the high magnesium is a problem with the salts you are using, rather than a problem with a two part that works to maintain it where it is.

If you used the two part exactly as designed (using the recommended amount of magnesium part), the dose added would be boosting magnesium about 2 ppm per day (ignoring effects of water changes).

So I recognize there is a conundrum here that has no perfect solution (at least not one solved without a chemist fiddling with several dosing chemicals).

It is OK, but not really perfect, to ignore dosing the magnesium part when magnesium is already too high for some reason.

 

[navathehutt]

My DIY two part (which you are using), like most commercial two parts (e.g., B-ionic by ESV) is designed to maintain magnesium where it is, and not to boost it or deplete it. Unfortunately, people see the magnesium with my DIY and don't see it so don't stress out over it when using commercial two parts, CaCO3/CO2 reactors, etc.

Of course, if you do not use the magnesium part, the levels will become lower than if you used it. You are probably depleting magnesium by about 1-2 ppm per day, at which rate it takes a long time to see with a kit.

Assuming the high values are accurate (which they may not be), the high magnesium is a problem with the salts you are using, rather than a problem with a two part that works to maintain it where it is.

If you used the two part exactly as designed (using the recommended amount of magnesium part), the dose added would be boosting magnesium about 2 ppm per day (ignoring effects of water changes).

So I recognize there is a conundrum here that has no perfect solution (at least not one solved without a chemist fiddling with several dosing chemicals).

It is OK, but not really perfect, to ignore dosing the magnesium part when magnesium is already too high for some reason.

Thanks randy i had this same question, I was using the All 4 Reef - all in one dosing a very small amount and was wondering if my mag would keep going up. I just did some large water changes so I'm probably maxed out in mag levels

 

[Mark18]

Hi Randy

After a 20 year hiatus in reef keeping, I recently purchased a 48L nano AIO tank. The aquarium was already established with a pair of 2-3 yo ocellaris clowns and some live rock.

Anyway, after 10 days and weekly 50% NSW changes, I tested the tank and the Alkalinity had dropped to 6.4, so started dosing with your recipe No2 for Alk and Cal. I slowly got Alk up to 8dkh before testing the Cal which was on 450ppm (a bit high-target 420ppm), I calculate 420ppm in next 2 days.

As I hadn’t been dosing Mag, I bought a Salifert test kit at weekend. Tested on Sat - 1410ppm, I thought that was high. Tested on Sun at same time as previous test - 1440ppm! So decided to test the NSW I use, tested 1395 ppm. I thought NSW was 1280ppm?

Do you think this test kit is reading 9% over actual given I haven’t been dosing Mag, I don’t see why it would be high otherwise? Also I can’t see the LFS dosing the NSW they sell given they get it direct from the ocean!

PS I’m in Australia

 

[fishnugget1]

My mag is at 1500 and all of a sudden my calcium is stuck at 470. I have not been dosing calcium in over a week. I used to dose 70 along with my alkalinity at 80. Should I do a water change to lower mag? Should I change out some tank water with straight R/O/ Salinity .026-.027 I am using ESV Bioinc.? My all is 8.5

 

[jebernier]

Thanks randy i had this same question, I was using the All 4 Reef - all in one dosing a very small amount and was wondering if my mag would keep going up. I just did some large water changes so I'm probably maxed out in mag levels

Hey, having the same issue with All-for-Reef, high Magnesium levels. Did you ever figure out the issue? Areyou still using All-for-Reef?
John

 

[Randy Holmes-Farley]

Hey, having the same issue with All-for-Reef, high Magnesium levels. Did you ever figure out the issue? Areyou still using All-for-Reef?
John

How high?

Are you using the Red Sea kit?

 

[tidefanjam]

I use the all4reef also, and i have the same issue in that my cal and mag are very high, not sure if its really a problem or not, everything seems ok. my cal reads 490 with the red sea and my mag is 1450 on the salifert

 

[135zman]

Same high Mg situation here with All 4 Reef on 135 gallon cube mixed reef with medium sized SPS and heavy coralline algae. I also use an Avast Kalk stirrer dosing at less than daily evaporation rate in order to decrease daily All 4 Reef dosing levels. Corals definitely look better in coloration, polyp extension and growth since switching to All 4 Reef over a year ago so I don’t want to switch back to BRS 2-part, but the high Mg is concerning.

As of 3/20/21, All 4 Reef dosing is at 38ml per day (reduced from 40ml) with recent Alk ranging between 8.6 to 9.0 (average of Hanna and Salifert), Calcium 468 (Hanna) and Mg at 1500 (Salifert). Last month ICP test results were Alk at 9.19, calcium 488, and Mg 1437. After the ICP results, I turned All 4 Reef doser off for 2 days to bring Alkalinity down and then set at the lower 38ml daily dosing. Alk and Calcium levels came down, but Mg is now at 1500.

Any suggestions? Looping in @Lou Ekus since he has been very helpful in the past for TM product questions.

 

[schuby]

For clarity, NSW = "Natural Sea Water" and ASW = "Artificial Sea Water".

 

[Randy Holmes-Farley]

I use the all4reef also, and i have the same issue in that my cal and mag are very high, not sure if its really a problem or not, everything seems ok. my cal reads 490 with the red sea and my mag is 1450 on the salifert

How are you deciding how much of the All for Reef to dose?

Maybe you are just overdosing.

 

[Lou Ekus]

@135zman This is why I say that personally, I like to use the Ca as the dosage indicator for the AFR rather than the alkalinity. If you use the Ca as the dosage indicator and the alkalinity is lagging down, then some regular small addition of alkalinity will solve the issue. If you use the alkalinity as the dosage indicator, then there is always the possibility that your tank is one of those that uses more alkalinity per unit of Ca than the corals use. In that case, the alkalinity will be correct, but the Ca and Mg may end up high. This seems to be the case for you. I would suggest a slightly smaller AFR dose and some additional dose of alkalinity like sodium carbonate or sodium bicarbonate. If your try to supplement with Kalkwasser, then you are also increasing Ca, and things can still get out of balance.

 

[135zman]

Thanks Lou! Curious about the difference in the other TM combined Alkalinity and Calcium products like CarboCalcium or Bio-Calcium. I’ve read the webesite description, but I can’t figure our how they differ.

In my tank situation with using more Alk than Calcium, would either of these products still cause Mg to still rise if dosing to maintain steady Alk? Do they even contain Mg? I know the supply chain for All 4 Reef is an issue and I only have one bottle on hand, so thinking I might have to make a switch in the next few weeks.

 

[tidefanjam]

How are you deciding how much of the All for Reef to dose?

Maybe you are just overdosing.

maybe, I went by the instructions and have used my alk,trying to keep it at about 8.5, to adjust the dosage to the 30ml I'm dosing now, after reading the above comments I may need to adjust by the cal instead
my tank is a 120 mixed, tho mostly LPS, with with a 30ish gallon sump, probably about 115 gallons water volume after accounting for rock, etc.

 

[Randy Holmes-Farley]

maybe, I went by the instructions and have used my alk,trying to keep it at about 8.5, to adjust the dosage to the 30ml I'm dosing now, after reading the above comments I may need to adjust by the cal instead

Which is why I asked. If not all of the formate is showing up as alkalinity, dosing by alkalinity can lead to overdosing.