Problems with maintaining magnesium it keeps dropping.

Aqua Nomad

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There is no problem in your measuring or the Mg products, the "problem" is elsewhere, something is consuming the Mg. We have found many people with these same problems and it seems to be always the same age tanks 1-2 year old. There is something that consumes that Mg and will last some time, but after that, the consumption turn to normal. The thing is that we would like to know why is that? also, we think that more people have this same problem ( they just don`t know it ) but unfortunately, not many hobbyists measure the Mg consumption.

If someone know the reason for this happening we would like to know also, and learn something new :)
 
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Hellybell80

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Have you tried testing your fresh salt mix, if the salinity is correct then Tropic Marin should be near enough 1350ppm for magnesium, least you will know if your test kit is correct.
Yup a couple of months ago. A freshly mixed batch.
 
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Hellybell80

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In fact I have a icp result test that pretty much matches my home test.
Screenshot_20210103-232731_Acrobat for Samsung.jpg
 

Jonify

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Have you noticed if your tank is using less calcium or you're requiring less dosing of Ca and Alk? What's your daily consumption rate of those two?

I also seem to remember an article from RHF that described the Mg ion as being a substitute for something else if it weren't readily available, but I forget what that was. He has also talked elsewhere of reactions that cause magnesium hydroxide precipitates ... if that were happening, I assume your Mg would be dropping as well, though I do not know, or did not see, what the rate of precipitation would be or how that would reduce available Mg in your tank.

Several other interesting articles here that I had originally tried to interpret, but figured it was best left to you ... they describe a couple of different age- or water condition-related changes in the way coral use Mg.


 
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Randy Holmes-Farley

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Randy Holmes-Farley

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Two different tanks and almost no consumption in Ca and Alk but Mg have to add every day to keep it up 1350 range. They are both using different products ( DSR for 800L tank and Tropic Marin All-For-Reef for 500L tank ). For the 800L tank, you have to add 340ml Mg/day and same time 0ml Ca and 30ml KH ( DSR ). For the 500L tank, you have to add 120ml ( Fauna Marin Mg ) and All-For-Reef 80ml to keep the ionic balance.

How can you claim no consumption of calcium when the products you mention dosing contain calcium?

All it means that that those products may not have added enough magnesium to balance the calcium in them.

Tropic Marin suggests this can be the case with All For Reef, since magnesium incorporation relative to calcium depends strongly on what is using it. Coralline algae uses a low more magnesium relative to calcium than many corals
 
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Randy Holmes-Farley

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It was more to point out that my testing was in line with the icp test. As was stated before it could be due to me not testing accurately.
I just can't keep it there without a larger dose. ☹

It is not from excessive consumption. As some folks have noted, that cannot happen in an ordinary reef aquarium. There is no place for it to go.

Real magnesium consumption is not more than about 1/10th of the calcium consumption, or about 1-2 ppm per day. Anything substantially higher is test error, caused by water changes with a low magnesium mix, or due to salinity changes.

Many folks are also surprised how much additive it takes to actually boost magnesium buy even a few ppm, but that is just a perception issue, not excessive magnesium consumption.
 

Aqua Nomad

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How can you claim no consumption of calcium when the products you mention dosing contain calcium?

All it means that that those products may not have added enough magnesium to balance the calcium in them.

Tropic Marin suggests this can be the case with All For Reef, since magnesium incorporation relative to calcium depends strongly on what is using it. Coralline algae uses a low more magnesium relative to calcium than many corals
Yes, I know they contain calcium, but as you can see those people have to add so much more in Mg comparing to the ca consumption. But I think that the answer is definitely correlating in coralline algae consumption in a tank that has very little actual corals in the tank. They are about the same age and what I have seen in the pictures of those tanks they are definitely now in the process of making more coralline algae now those parameters are starting to be corrected in multiple weeks.
 

Randy Holmes-Farley

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Yes, I know they contain calcium, but as you can see those people have to add so much more in Mg comparing to the ca consumption. But I think that the answer is definitely correlating in coralline algae consumption in a tank that has very little actual corals in the tank. They are about the same age and what I have seen in the pictures of those tanks they are definitely now in the process of making more coralline algae now those parameters are starting to be corrected in multiple weeks.

The skeleton of coralline algae is about 4.4% magnesium by weight, while most corals are 0.1 to 3% magnesium by weight (see the Table in my article below). These same skeletons contain about 30-40% calcium).


 

Aqua Nomad

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The skeleton of coralline algae is about 4.4% magnesium by weight, while most corals are 0.1 to 3% magnesium by weight (see the Table in my article below). These same skeletons contain about 30-40% calcium).


Thanks Randy. I have read that articles 2-3 times before ( little bit technical text and English is not my main language ) that's the best article on Mg that I have found so far :)
 
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Randy Holmes-Farley

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I also have this same "issue" My alk and cal are stable but my mag slowly goes down and requires a crap ton of mag solution to get it back up.

How much of a drop over what time period?

Note that even a drop within test error of a mag kit can take large amounts of additive to "fix". It's just the nature of the highest concentration ion that we supplement, combined with marginal testing capability and dry solid additives that are only around 10% magnesium by weight.

There's no possible sink for substantial magnesium in a reef tank that does not take out calcium and alkalinity too.

Thus, any change you see (when alk and calcium are stable without dosing them) can only be from:

1. Test error (very common)
2. Water changes with a mix not matching the tank in magnesium (have you measured your new salt water?)
3. Changes in salinity (drop from sg = 1.026 to 1.025 will drop magnesium in seawater from 1300 to 1250 ppm)
4. Calcium and alk are being consumed, but are added back in some way you may not recognize
 

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1. Ive tested Mag many times and the results are in the same realm.
2. I have not tested the new SW for Mag. (Will do that)
3. I have been slowing bringing up my salinity from 1.024 to 1.026. The stock ATO from Redsea sucks and keeps placing too much FW.
4. I used to dose Alk but had to stop months ago because my consumption seemed to stop. Maybe this is because I started doing weekly water changes?
 

Randy Holmes-Farley

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1. Ive tested Mag many times and the results are in the same realm.

Magnesium test kits have a pretty wide range of results (in a ppm variability sense) even when functioning perfectly.
 
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I don’t have a magnesium issue, yet. I’m working on stabilizing my tank before introducing acropora. My magnesium tested at 1140 (I did 3 tests at 3 different times in the same day) using salifert. I have not tried supplementing it yet, as I want to see what to do before I start dosing.

my alk is 7.7 and calcium is 380. All I have in my tank is a couple softies, (zoas, toadstool) and 1 acan. I also run a Algae turf scrubber so I don’t know if that’s what is depleting it. I did a 55gallon water change (Red Sea blue bucket for salt) on my 220g tank just 5 days ago. Sg is 1.026.
There’s no way my tank is consuming much - alk and ca test the same daily, without dosing anything. The mag is low though.
 

Randy Holmes-Farley

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I don’t have a magnesium issue, yet. I’m working on stabilizing my tank before introducing acropora. My magnesium tested at 1140 (I did 3 tests at 3 different times in the same day) using salifert. I have not tried supplementing it yet, as I want to see what to do before I start dosing.

my alk is 7.7 and calcium is 380. All I have in my tank is a couple softies, (zoas, toadstool) and 1 acan. I also run a Algae turf scrubber so I don’t know if that’s what is depleting it. I did a 55gallon water change (Red Sea blue bucket for salt) on my 220g tank just 5 days ago. Sg is 1.026.
There’s no way my tank is consuming much - alk and ca test the same daily, without dosing anything. The mag is low though.

If it is low and that result is not test error (a test can repeat perfectly and still be inaccurate) then it is coming from the salt mix. It is not being consumed.

Low salinity can also yield low everything, including magnesium. What do you think the salinity is and how are you measuring it?
 

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