Magnesium Question

[themcfreak]

Hello all! I have just spent hours reading over various threads. It's so addicting! But it also brought to my attention that I have a question, hopefully an easy one that Randy can chime in on. If it has been answered before I apologize, I promise I searched, just so many articles to comb through to find the same exact question I had.

I dose 2 part (BRS aka Randy's recipe), and have for almost a year now. I have dose about 30 ml a day of each with a DOS spread pretty evenly and spread apart so that neither of them are entering tank at same time. However, I have never dosed the magnesium. BRS (if I remember correctly) says to dose a gallon of mixed Mg after you finish the gallon of Alk/Ca, but I have failed to do that. However, my testing shows my Mg constantly in an acceptable range (around 1300ppm). I do use Red Sea, which I learned tonight is not as accurate, but I feel its probably close enough to still be in range. So question is, should I dose the full gallon of Mg anyway? Seems to me after reading that it won't actually raise Mg that much, so probably won't hurt? I do also use Red Sea Coral Pro salt, and dose 5L daily with a DOS doing AWC, so does have a source of Mg in it, so is that enough, or should I dose the Mg anyway?

Edit: It is a 42 gallon tank, with ~10 gallons in sump.
Testing parameters are pretty normal I think (All tested with Red Sea test kits)
Salinity: 1.025
Alk: 9.5
Ca: 410
Mg: 1400 at last test
Nitrates: Between 2-5 ppm
Phosphates: Between 0-0.02 ppm

Thanks in advance, and if you see this Randy, please know that people like me are forever in your debt for all the amazing articles and feedback and advice and recipes and everything else you do. It is greatly appreciated, and thanks cannot be given in enough quantity (not even with sufficient constant dosing!) haha

 

[Randy Holmes-Farley Verified Community Expert]

I dose 2 part (BRS aka Randy's recipe), and have for almost a year now. I have dose about 30 ml a day of each with a DOS spread pretty evenly and spread apart so that neither of them are entering tank at same time. However, I have never dosed the magnesium. BRS (if I remember correctly) says to dose a gallon of mixed Mg after you finish the gallon of Alk/Ca, but I have failed to do that. However, my testing shows my Mg constantly in an acceptable range (around 1300ppm). I do use Red Sea, which I learned tonight is not as accurate, but I feel its probably close enough to still be in range. So question is, should I dose the full gallon of Mg anyway? Seems to me after reading that it won't actually raise Mg that much, so probably won't hurt?

Nooooo! Not a gallon. 610 mL. In a smaller tank, spreading that 610 mL out is also advisable.

The Red Sea coral pro is boosting magnesium quite high, and using the advised dose would keep it there. If you want it lower, it is OK to dose less or not at all. Not doing it will allow mag and sulfate to drop a bit. Neither is likely a huge problem, but I would advise adding it as the original recipe (mine) calls for.

You can measure the expected mag boost with the calculator (enter Randy Recipe 1):

http://reef.diesyst.com/chemcalc/chem_calc3.html

 

[themcfreak]

Oh, sorry. Haha basic math does say that 610 mL is not 1 gallon. In regard to my Alk/Ca dosing, I do end up with a white layer of precipitant (at least I assume that is what it is) in the sump chamber where the 2 are dosed. Is it possible Mg would help minimize this? I thought I was overdosing the Alk/Ca which led to the precipitation (again, only in 1 place), but I tried to cut back on dosing, and all that did was hurt my numbers. It may have limited precipitation, but I feel I would rather have stable parameters over a little white layer in the bottom of a sump chamber. Or am I looking at that the wrong way?

 

[Shadowspop]

Nooooo! Not a gallon. 610 mL. In a smaller tank, spreading that 610 mL out is also advisable.

The Red Sea coral pro is boosting magnesium quite high, and using the advised dose would keep it there. If you want it lower, it is OK to dose less or not at all. Not doing it will allow mag and sulfate to drop a bit. Neither is likely a huge problem, but I would advise adding it as the original recipe (mine) calls for.

You can measure the expected mag boost with the calculator (enter Randy Recipe 1):

http://reef.diesyst.com/chemcalc/chem_calc3.html

Hey Randy, great calculator. I'm kinda in the same boat. Just checked my Mg for the first time and it's 1250. I'm shooting for 1450. Red Sea Mg says to add over 60 ml. It's only a 50ml bottle, is that possible? I don't see Red Sea as an option on your calculator.

 

[Luno]

I dunno how good it actually is but it works for me, I dose to keep my levels where I want them. Alk at 8 calcium at 420 and mag at 1400. Mag gets used less so it's dosing doesn't happen anywhere near as much. But I do dose it regularly to keep 1400. Again dunno if it's the right thing to do but it works for me

In a hobby that's focused around stability that is key for me

 

[Randy Holmes-Farley Verified Community Expert]

Hey Randy, great calculator. I'm kinda in the same boat. Just checked my Mg for the first time and it's 1250. I'm shooting for 1450. Red Sea Mg says to add over 60 ml. It's only a 50ml bottle, is that possible? I don't see Red Sea as an option on your calculator.

It takes very large amounts to boost magnesium, but I don’t know the Red Sea concentration.

 

[Shadowspop]

It takes very large amounts to boost magnesium, but I don’t know the Red Sea concentration.

So over what period should I raise it from 1250-1450?

 

[Randy Holmes-Farley Verified Community Expert]

So over what period should I raise it from 1250-1450?

Depends on the purity of your additive (since, IMO, impurities are the concern with a fast rise, not the magnesium), but I'd suggest a few days should be OK if using a quality material.