Really need help with Magnesium dosing

[FreshSaltyGuy]

Hi All,

Can really use someone's help with Magnesium dosing. I have a 250 gal total water bill with Simon included mixed reef tank. My Mag has been low for a while since I neglected my tank. Working on getting it back to where it should be which I'm shooting for 1400ppm.

My current Magnesium is 1110pm measured over the last week with a Salifert Tester. Salinity is currently sitting at 34.

I happen to have a 1.2kg jar of Seachem Reef Advantage Magnesium that I wanted to use. Yes I know I need A LOT. As per the Seachem Magnesium Calc it shows that I need 3,443.8g or 688tsp.
It says the most I should dose is 300g or 46.9tsp per day for my size tank roughly.

What I can't figure out is how much TOTAL rodi water do I mix the entire 1.2kg jar in? And can I use an auto doser to dose the how many ML per day?
Or am I thinking of this all wrong?

Please help my head hurts! Thanks

 

[rishma]

Hi All,

Can really use someone's help with Magnesium dosing. I have a 250 gal total water bill with Simon included mixed reef tank. My Mag has been low for a while since I neglected my tank. Working on getting it back to where it should be which I'm shooting for 1400ppm.

My current Magnesium is 1110pm measured over the last week with a Salifert Tester. Salinity is currently sitting at 34.

I happen to have a 1.2kg jar of Seachem Reef Advantage Magnesium that I wanted to use. Yes I know I need A LOT. As per the Seachem Magnesium Calc it shows that I need 3,443.8g or 688tsp.
It says the most I should dose is 300g or 46.9tsp per day for my size tank roughly.

What I can't figure out is how much TOTAL rodi water do I mix the entire 1.2kg jar in? And can I use an auto doser to dose the how many ML per day?
Or am I thinking of this all wrong?

Please help my head hurts! Thanks

I am not familiar with that product but I have a couple of comments to offer.

First, magnesium home tests are so frequently inaccurate to be arguably not helpful. I have not tested magnesium in years except what I get in an occasional ICP. I’d be wary of adding that much magnesium based on a home test kit result.

Randy frequently suggest testing newly mixed saltwater to see if your magnesium test kit is reasonable.

I suggest looking at this thread.
https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/

 

[Randy Holmes-Farley Verified Community Expert]

I recommend using your kit in new salt water to see if this roughly accurate, but on the specific question about how much ro/di: it doesn’t matter as long as it dissolves. It is very soluble.

If you do proceed to raise it, go slow. There’s no rush and 25 ppm per day is all I’d do.

 

[FreshSaltyGuy]

I recommend using your kit in new salt water to see if this roughly accurate, but on the specific question about how much ro/di: it doesn’t matter as long as it dissolves. It is very soluble.

If you do proceed to raise it, go slow. There’s no rush and 25 ppm per day is all I’d do.

Ok but if I put it in say 1/2 gallon of water vs. 1 gallon, isn't it much more concentrated? So how do I determine 25ppm?

 

[FreshSaltyGuy]

I am not familiar with that product but I have a couple of comments to offer.

First, magnesium home tests are so frequently inaccurate to be arguably not helpful. I have not tested magnesium in years except what I get in an occasional ICP. I’d be wary of adding that much magnesium based on a home test kit result.

Randy frequently suggest testing newly mixed saltwater to see if your magnesium test kit is reasonable.

I suggest looking at this thread.
https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/

I will try that and check it. Salifert hasn't really ever let me down yet. Also, probably good to not that I DO NOT do any water changes. I haven't done one on this tank in over a year and everything is beautiful, just not growing as fast as I'd like it to lol.

 

[Randy Holmes-Farley Verified Community Expert]

Ok but if I put it in say 1/2 gallon of water vs. 1 gallon, isn't it much more concentrated? So how do I determine 25ppm?

If you know the boost from the dry powder you measure out, then when you add to the tank however much water you dissolved it in, you get that boost. If you use twice as much water, you still need to add it all to get that boost.

 

[rishma]

I will try that and check it. Salifert hasn't really ever let me down yet. Also, probably good to not that I DO NOT do any water changes. I haven't done one on this tank in over a year and everything is beautiful, just not growing as fast as I'd like it to lol.

Salifert is a good brand. But I doubt any brand for magnesium.

To put it in perspective, if your magnesium was 1350 a year ago, and now is 1110 w ith no water changes, that would correlate to 1.8-3.6 dKH per day alkalinity consumption. If that makes sense for your tank then it’s reasonable.

 

[FreshSaltyGuy]

Salifert is a good brand. But I doubt any brand for magnesium.

To put it in perspective, if your magnesium was 1350 a year ago, and now is 1110 w ith no water changes, that would correlate to 1.8-3.6 dKH per day alkalinity consumption. If that makes sense for your tank then it’s reasonable.

Thanks has been up since Oct. 2023 so honestly still understanding what it uses etc...especially since I have added a lot of corals since then

 

[rishma]

Thanks has been up since Oct. 2023 so honestly still understanding what it uses etc...especially since I have added a lot of corals since then

Understood. The portions I quoted above will not vary by tank. They are true for all tanks with calcifying corals and coraline algae.

 

[Reefering1]

You would know if you have 1.8 - 3.6dkh demand...

 

[rishma]

You would know if you have 1.8 - 3.6dkh demand...

Ah. I see. I misunderstood.

 

[Miami Reef]

I recommend using your kit in new salt water to see if this roughly accurate, but on the specific question about how much ro/di: it doesn’t matter as long as it dissolves. It is very soluble.

If you do proceed to raise it, go slow. There’s no rush and 25 ppm per day is all I’d do.

We should bottle up natural seawater and use them as magnesium standards. Do you think magnesium varies in NSW? I have a bottle of a NSW that I use as a mag standard. Salifert tests around 1280. It’s actually extremely precise (tested 5 times.)

Also, if someone doses high pH alk solutions, but allowed the magnesium hydroxide to settle and precipitate from very little flow in the sump, would that be a substantial magnesium sink?

 

[rishma]

We should bottle up natural seawater and use them as magnesium standards. Do you think magnesium varies in NSW? I have a bottle of a NSW that I use as a mag standard. Salifert tests around 1280. It’s actually extremely precise (tested 5 times.)

Also, if someone doses high pH alk solutions, but allowed the magnesium hydroxide to settle and precipitate from very little flow in the sump, would that be a substantial magnesium sink?

That’s a good idea! If I ever get the urge to test magnesium I’ll go to the beach first

 

[Reefering1]

Ah. I see. I misunderstood.

I don't think you did... I was saying op would know if he had that kind of demand.

 

[Randy Holmes-Farley Verified Community Expert]

We should bottle up natural seawater and use them as magnesium standards. Do you think magnesium varies in NSW? I have a bottle of a NSW that I use as a mag standard. Salifert tests around 1280. It’s actually extremely precise (tested 5 times.)

That will work and there are standards available. But I think it is perhaps cheaper to bottle tank water, get an ICP, then use that bottled tank water as a standard.

But here's a type of standard. I had a couple of them that American Marine/Pinpoint once gave me (though not the exact product linked below).


https://osil.com/product/atlantic-seawater/
That material can act as a standard for any major ion which are known to only vary by salinity.

 

[Randy Holmes-Farley Verified Community Expert]

We should bottle up natural seawater and use them as magnesium standards. Do you think magnesium varies in NSW? I have a bottle of a NSW that I use as a mag standard. Salifert tests around 1280. It’s actually extremely precise (tested 5 times.)

Also, if someone doses high pH alk solutions, but allowed the magnesium hydroxide to settle and precipitate from very little flow in the sump, would that be a substantial magnesium sink?

If it didn't redissolve, yes. But magnesium hydroxide should redissolve into seawater at reef tank pH.

 

[UMALUM]

I am not familiar with that product but I have a couple of comments to offer.

First, magnesium home tests are so frequently inaccurate to be arguably not helpful. I have not tested magnesium in years except what I get in an occasional ICP. I’d be wary of adding that much magnesium based on a home test kit result.

Randy frequently suggest testing newly mixed saltwater to see if your magnesium test kit is reasonable.

I suggest looking at this thread.
https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/

No offense, but YOUR constant RMM push every time the word magnesium comes up is getting a little cringe. I'll bet you $50 to a doughnut there's been more threads on red sea failures than bad salifert mag kits. Notice how the man behind the method only gave advice on what was relevant? Yes RMM makes sense actually I would call it borderline common but gaslighting people and telling them not to test is a false narrative.

 

[rishma]

No offense, but YOUR constant RMM push every time the word magnesium comes up is getting a little cringe. I'll bet you $50 to a doughnut there's been more threads on red sea failures than bad salifert mag kits. Notice how the man behind the method only gave advice on what was relevant? Yes RMM makes sense actually I would call it borderline common but gaslighting people and telling them not to test is a false narrative.

Wow. That’s quite a response.

Every time someone comes and posts about issues with magnesium based on home test results, I think it’s good advice to point them there. You can disagree, and feel free to state so the OP get a different view point.

And I am not telling people not to test, I think it’s better to use a more reliable test method and just use a little math to get there. I also suggested the OP test his newly mixed saltwater to see if his magnesium test kit was reasonable. Not sure what your beef is.

In this case the OP was considering how to dump a huge amount of magnesium into his tank based on a salifert test kit. I think a little caution to not blindly trust that kit is well placed.

You have yourself a fine day.

 

[Randy Holmes-Farley Verified Community Expert]

No offense, but YOUR constant RMM push every time the word magnesium comes up is getting a little cringe. I'll bet you $50 to a doughnut there's been more threads on red sea failures than bad salifert mag kits. Notice how the man behind the method only gave advice on what was relevant? Yes RMM makes sense actually I would call it borderline common but gaslighting people and telling them not to test is a false narrative.

Any reports of RMM failures?

 

[UMALUM]

Any reports of RMM failures?

Seems unlikely anyone would know with the instructions being not to test.