Ca X 3 = MG value

bundy13

New member
Is this always true? so whatever my CA.is i just multiply times 3 and thats my MG?


So do i really need tp be testing MG. ?
Or does this always work

thank
 

RC Jet Flier

In Memoriam
just because your Ca is XX ppm, doesn't mean the Mg is also XX ppm, the only relationship is if Mg is low enough (IME below 700ish) then the Ca levels are difficult to impossible to get above 250ish ppm and stay there.

NSW levels of Mg are 1300-1500 ppm, Ca levels 425-450 ppm, try to keep your system in those ranges.

this 3x idea is about as useless as the X watts per gallon for lighting :rolleyes:
 
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tmz

ReefKeeping Mag staff
Premium Member
At a salinity of 1.025 Natural Seawater NSW has magnesium at 1285ppmand calcium at 400ppm(roughly 3.25 to one).A proper level of magnesium makes it harder for precipitation to occur and thus makes it easier to maintain calcium.
It is also important to note that alkalinity plays a key role in the calcification process. NSW alkalinity is 2.1 to 2.5 meq/l or 6to 7dkh. Without balanced alkalinity calcium will not be used by your corals.

Using kalk water for calcium and alkalinity promotes growth and therefore magnesium uptake and depletion since corals use magnesium in creating their skeletons in addition to calcium and carbonate
So,balance between these 3 keys:magnesium,calcium and alkalinity (carbonate and bicarbonate)is necessary for coral health and growth. A good bench mark at 1.025 salinity is 1350magnesium with 425calcium and 3.25meq/l(9.1dkh)
 

JetCat USA

In Memoriam
<a href=showthread.php?s=&postid=10490017#post10490017 target=_blank>Originally posted</a> by tmz
At a salinity of 1.025 ....................at 1.025 salinity

Not to be overly picky, but you're making references to specific gravity, not salinity. the salinity of NSW is 35 ppt. SG is temperature dependent, salinity is not.
 

reefnetworth

Premium Member
i read then printed RH-F's, NSW comparison to Reef tanks.
the article also states that it depends on where your NSW is being measured (worldwide it ranges) and the inhabitants of the Reef tank may need more or less than NSW parms. :)
 

bertoni

Premium Member
There isn't any reason to keep magnesium at 3x calcium. That doesn't make much sense to me. I'd keep each parameter in its acceptable range, and ignore the ratio.
 

tmz

ReefKeeping Mag staff
Premium Member
My numbers are from Sprung and Delbeek," the Reef Aquarium Volume 3". I agree that it depends on where the NSW is measured since it also depends on the salinity with different seas at different ppt(the authors chose to use sg in thier description-so did I). All of the numbers put forth by everyone aren't far apart so I don't really see this as a debate.For me the more discussion on these points the better my understanding.Incidentally Randy Homes Farley is referenced extrensively in this book.
I also agree that some variability from whatever nsw standard you choose may be necessary in a specific reef tank . One good reason to go a little higher on the three keys calcium,magnesium and alkalinity provided you can keep them in balance(ie pproportionate to each other) is the relatively smalll amount of water we are using. A coral reef is a pinpoint in a very large body of water so it won't deplete these elements. Our captive environments on the other hand can fluctuate quickly.
Tom
 

Billybeau1

Premium Member
Generally, If one has the proper equipment to test general hardness in salt water, Once you know your calcium level, you can subtract Ca++ from GH and the rest is Magnesium.

I think this is where everyone is getting confused. :)
 

bertoni

Premium Member
Upon rereading the original question, more answer:

No, magnesium is not always 3x calcium. Magnesium varies largely independently of calcium, depending on its rate of consumption and supplementation.
 

JetCat USA

In Memoriam
<a href=showthread.php?s=&postid=10493678#post10493678 target=_blank>Originally posted</a> by Billybeau1


I think this is where everyone is getting confused. :)

the confusion seams to come from allot of posters who regularly post that your Mg should be 3x your Ca. if your Ca is 400, they say your Mg should be 1200, if you run a Ca of 500, they think your Mg should be kept at 1500..............will that mentality work? sure but it's not a general rule of thumb but seams to be getting pushed as such the past yr or so.
 

littleoldme

New member
Ca X 3 = MG value

It was referenced a few times by Anthony Calfo in the all things salty forum when he was on the board.
 

Billybeau1

Premium Member
Re: Ca X 3 = MG value

<a href=showthread.php?s=&postid=10493966#post10493966 target=_blank>Originally posted</a> by littleoldme
It was referenced a few times by Anthony Calfo in the all things salty forum when he was on the board.

I question his thinking in that statement, if indeed he said it.

There are general guidelines to keep calcium, alkalinity and magnesium levels in a reef tank. Although the numbers seem to jive at the recommended levels, if one is out of the norm, there is no reason to adjust the other to 3x.
 

tmz

ReefKeeping Mag staff
Premium Member
How does general haredness differ from total alkalinity and how do you test for it? I don't subscribe to the 3x theory but I think I can see some logic in it. None of the levels stands alone calcium,alkalinity and magnesium are interdependent . Only so much can be held in solution so if one is too high or low another is likely to be out of balance. Therefore proportions are important.Since sea water has magnesium at about 3.25 to 1 of calcium, the 3x as as a short hand for their proportions may be useful .
 

bertoni

Premium Member
I'm not sure why you think the proportions are that important. Could you please specify what you think is going to happen if the proportions vary?
 

tmz

ReefKeeping Mag staff
Premium Member
If for example magnesium is too low you won't be able to maintain high levels of calcium since percipitation will occur sooner. If alkalinity is too high you won't have room in solution for a high level of calcium. If alkalinity is too low,high calcium will not be useable . Proportions are a way of expressing balance. I think it would be a good thing to replicate the natural proportions and amounts of key elements whence a specimen came. I know I can't do this within the small puddle of water I try to manage with aquarium hobby grade tests and supplements,particulary since consumption rates deplete elements quickly in this small enviroment. So I settle for ranges but as a trio not independently.If I'm high side on calcium I wan't
to be high side on magnesium and alkalinity in a similar fashion.
 

bertoni

Premium Member
I don't see any relationship between calcium and magnesium that constitutes an issue as long as they are both in the acceptable range. I don't see what will happen if they are at opposite ends of their ranges, for example. Same thing for alkalinity and calcium, for that matter.
 

tmz

ReefKeeping Mag staff
Premium Member
Well I suppose each has his own way of looking at thingsand I believe this whole discussion is becoming somewhat semantical.
I would note,however, that Sprung and Delbeek along with Fareley extensively discuss balancing alkalinity and calcium and offer strategies such as adding buffer or calcium alternately to reach desired balances. There are many pages and graphics dedicated to this issue which speak to precise levels within the ranges in The Reef Aquarium Volume 3. So I respectfully disagree with your position unless you can sustantiate your belief that precision in balance is of no consequence.If you can I truly would like to learn. It has always been my understanding from reading these gentlemen and others that balance is very important.Your position seems to be that quantities of these elements only need to be only somewhat proportionate.
 
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