Getting the ions right: Do you dose magnesium?

[Treefer32]

At Randy's recommendation I dose Magnesium Chloride mixed with Magnesium sulfate. I don't know the chemistry (I nearly failed advanced chem), but my understanding is that sulfates balance out the chlorides. So, I mix and dose both daily. Everytime I test mg (once a year or so) it's always 1500-1550. I go through a gallon of the mixed solution every 2 months or so. I did 1/3 amount of what I dose for alk and calcium as my daily regimen. Why you ask? Simly, because I didn't think I needed the same amount as alk and calcium, but I wanted some. So, I did around 1/3.

Alk and calcium stay very stable with calcium around 500-525 everytime I test and alk between 8.7 and 9.4 each time I test. (I test alk every 3-5 days). Calcium I test once a year.

 

[srobertb]

I have never had to dose magnesium. I don't check often but when I do it's always been 1400ish. I use a 50/50 mix of instant ocean and reef crystals

No need to say it because you summed it up. Stays around 1350-1400. I have it hooked up to a dosing pump but it’s off and has been for some time. I use tropic Marin pro reef and do continuous water changes.

 

[Randy Holmes-Farley]

I would also add that magnesium testing seems much more prone to substantial error than most other things we measure, and any individual may think they have a certain level, but actually may have a very different level.

That is easily proven by the many posts where people report different kits give very different values on the same water, and some folks report that magnesium goes up and down huge amounts day to day (it cannot).

I've been close to the opinion for years, and still am, that measuring magnesium may do more harm than good for most reefers, especially new reefers.

 

[homer1475]

I do weekly 20g WC on my 85g system with normal purple box IO. I have never dosed mag unless needed. MY WC's usually keeps it up, but I still have to dose it a couple times a year.

 

[Pridedcloth3]

I dose reef elixir and supplement fusion 2 part. So my tank gets its fill. Now if you ask if I measure it then that's a no. But I'm for sure getting some in there so I just let it be.

 

[Rowboman]

I tried calculating my consumption rate via weekly testing and setting it on a doser to keep as stable as possible and as Randy Homes-Farley said, the testing was too inconsistent to get it to work. Now I just add it to my Reef Crystals I use for water changes to bring the mix up to 1500 (I run it elevated for my SPS and euphyllia). Recently plumbed a frag tank in which I was running a level raised to 1700 with Kent tech M to kill bryopsis to my main display and killed the chaeto in my fuge as a result…. Woops ‍

 

[threebuoys]

I would also add that magnesium testing seems much more prone to substantial error than most other things we measure, and any individual may think they have a certain level, but actually may have a very different level.

That is easily proven by the many posts where people report different kits give very different values on the same water, and some folks report that magnesium goes up and down huge amounts day to day (it cannot).

I've been close to the opinion for years, and still am, that measuring magnesium may do more harm than good for most reefers, especially new reefers.

I recall this comment from other threads. I've been dosing 2 part for a year and I very seldom do significant water changes. I'm beginning to think maybe I should dose magnesium since I don't change water often. In light of the comment about difficulty measuring, would using a dose equal to 1/10 of what I use for calcium (magnesium from BRS 3 part kit) make sense? Or where should I start?

 

[chimbo84]

I use IO reef crystals and do water changes, maybe not regularly but it keeps my Magnesium up just fine.

In the future that may change and I'm already prepared for it.

I do the same. I have a can of Biomag on hand in case I need to boost it but regular water changes with reef crystals keeps it where I need it.

 

[hunterallen40]

I don't dose daily, but I do dose a correction every once and a while, usually when I see my trident has dropped to ~1320 ppm (from my target of ~1350 ppm).

I would also add that magnesium testing seems much more prone to substantial error than most other things we measure, and any individual may think they have a certain level, but actually may have a very different level.

That's something I was wondering about recently, actually. I did an Oceamo ICP-MS two months ago, and it registered my magnesium at close to1450 mg/L, which was rather surprising to me, as my trident was measuring around 1330 ppm. Usually those numbers are relatively close, but they weren't this time, so I decided to trust the ICP instead of the trident, and didn't dose any magnesium as a result.

I got my ICP test from last Friday back two days ago, and it registered by magnesium at 1286 mg/L (trident read it as 1310 ppm).

So my question is... @Randy Holmes-Farley in your experience, would ICP-MS testing be better than a titration-based approach for Magnesium? Is there any reliable way to determine the magnesium concentration?

 

[gbroadbridge]

Getting the ions right: Do you dose magnesium?

Magnesium helps with the balance of alkalinity and calcium, supports the health and growth of our corals, limits calcium carbonate precipitation, and more. One recommendation is to keep the magnesium levels between 1250 and 1350 although that may vary slightly. When trying to dial in your magnesium level, do you dose magnesium? Any tips to share on getting the magnesium correct in your reef tank? Let us know your thoughts on magnesium and any tips that you would like to share in the following discussion thread.

Photo by @FugeTown

I simply mix Mg in with my Ca and both get dosed together.

10g MgCl3 for every 50g CaCl3 works for me

 

[Dburr1014]

I use extra large arm in my carx and it says right on the package that it's high in magnesium. I don't really test for it but when I do it's 1,500+ sometimes I get a reading over 1600ppm with my aquaforest test kit.

 

[anabechara]

I dose AF 1+2+3+ using the recommended ratios. Been pondering bumping up the amount of mag in my mix as I have been hearing a lot about LPS liking elevated mag

I have heard that too, but unable to find real supporting evidence... do you have a scientific reliable source to that claim?
Also I have heard that high Mag can kill your snails... is that true?
I can tell you tho that my Hammer loves the mag in between 1450 and 1500...

 

[Dburr1014]

I have heard that too, but unable to find real supporting evidence... do you have a scientific reliable source to that claim?
Also I have heard that high Mag can kill your snails... is that true?
I can tell you tho that my Hammer loves the mag in between 1450 and 1500...

My snails are fine at high levels.

 

[zoomonster]

Said no but technically yes... I mix magnesium media with my calcium media in calcium reactor. I occasionally supplement with reef advantage magnesium powder (also use their strontium powder). Don't use any dosers though unless you want to count the Ca reactor.

 

[Eienna]

There need to be more options for "I don't, but I plan to" on these polls.

 

[vlangel]

I do weekly 8% water changes with purple box IO. I mix salt in a 55 gallon brute can and add a capful of 2 part alkalinity and calcium to the brute can. Probably every 4 or 5th brute can I add a capful of magnesium because my tank has a lot of macroalgae and years ago someone told me macros use magnesium. I don't know if that is true but my macros and softies, and LPS look great so it's working for me.

 

[slythy]

I dont notice any real mag swings. I keep it at 1400 and do 1gal awc each day.

only time i dose is when making new water to buffer it. Everythings auto on my tank but I havent needed to autodose cal

 

[Koigula]

FWIW, magnesium is consumed at most at about 1/10th of the rate of calcium consumption. Coralline causes a ratio that high. Some corals give a much lower ratio.

Thus, if you aren't dosing a lot of calcium, and especially if you do substantial water changes with a higher magnesium concentration, it may take a very long time to need to dose magnesium.

Many calcium and alk methods incorporate some amount of magneisum somehow, but it may not be enough depending on the organism mix in the aqaurium.

I used limewater (kalkwasser) which does not deliver magnesium, so I boosted the magnesium in the normal IO I used for automatic water changes, rather than ever dosing it directly to the tank.

I do same thing so interesting to see this!! I have tabling efflo on left I enjoy.

Specifically, I target 10% week of reef crystals and dose nightly stirred kalkwasser from Avast k1. Honestly, I do 10% water changes more consistently when nitrates approach 15 ppm by Hanna Nirate HR meter. I have found I can keep 1300 ppm Mag with mostly water changes so far. I add 50 cc BRS Soda Ash every few days to keep up also. There s no need for a calicum reactor now.

Would BRS Mag Mix for general adjustments be ok? What do you use?

 

[Randy Holmes-Farley]

I recall this comment from other threads. I've been dosing 2 part for a year and I very seldom do significant water changes. I'm beginning to think maybe I should dose magnesium since I don't change water often. In light of the comment about difficulty measuring, would using a dose equal to 1/10 of what I use for calcium (magnesium from BRS 3 part kit) make sense? Or where should I start?

My DIY (as BRS uses) has a fixed amount of part 3 to dose (1 mL of Part 3 per each 6.2 mL of the alk part OR per 6.2 mL of the calcium part), independent of any magnesium testing (unless magnesium is already too high for your preference).

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

 

[Randy Holmes-Farley]

I do same thing so interesting to see this!! I have tabling efflo on left I enjoy.

Specifically, I target 10% week of reef crystals and dose nightly stirred kalkwasser from Avast k1. Honestly, I do 10% water changes more consistently when nitrates approach 15 ppm by Hanna Nirate HR meter. I have found I can keep 1300 ppm Mag with mostly water changes so far. I add 50 cc BRS Soda Ash every few days to keep up also. There s no need for a calicum reactor now.

Would BRS Mag Mix for general adjustments be ok? What do you use?

There are a variety of recipes for DIY magnesium (like BRS sells).

For occasional adjustments, the exact recipe likely doesn't matter, but a recipe that is about 10 parts magnesium chloride and 1 part magneisum sulfate approximately amtches the seawater ratio of chloride to sulfate, and is a good choice (unless you are using this along with calcium by calcium chloride, in which case the optimal amount is less chloride and more sulfate (5:3).

Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

from it:

Using both Epsom salts and MAG flake, dissolve 7¼ cups MAG flake and ¾ cup Epsom salts in one gallon of water, and use that to supplement magnesium in amounts determined using this linked online calculator, with the entry "Randy's Recipes 1 and 2 Versions A and B," and ignore for this purpose what those designations mean. This recipe is preferred, but its advantage over recipe #2 is minimal in most cases.

Note that combining the two materials in solution can result in some precipitation of calcium sulfate (calcium and sulfate are impurities in the MAG flake and the Epsom salts, respectively. To assure yourself that the two materials have fully dissolved, dissolve each separately in some freshwater before combining them. Some calcium sulfate precipitation is acceptable, and it is okay to let the solids get into the aquarium, assuming you can dose in a way that prevents them from landing on delicate organisms.

Note also that this recipe (#3) is different from that given in my DIY two-part recipe, because in that case more magnesium sulfate is necessary to offset the rise in chloride that is provided by both the calcium chloride and the magnesium chloride.