Q for Randy (Magnesium additives)

[FSOL]

Hi Randy,

I got a question for you regarding a highly concentrated Mg additive.

I have to constantly add Mg. to my water to keep it around 1350ppm. I use Salifert's concentrated Mg. powder, but it's quite expensive AND not so concentrated enough. Using about 3 tablespoons of it only increases Mg concentration of 5 gallons of water by 150ppm. My tank has 220g of water, so using 3 tablespoons only increases my Mg concentration by 3.4ppm.

Is there a cheaper alternative to this?

Thanks

[ScottyDon't]

Magnesium chloride hexadrate as found in Randy's article here....
http://www.reefkeeping.com/issues/2006-02/rhf/index.php

[Randy Holmes-Farley]

If you are not otherwise using calcium chloride (such as in the DIY two part system), then a slightly different ratio of MAG flake to Epsom salts is preferable:

A Homemade Magnesium Supplement
http://web.archive.org/web/20001017132000/http://www.animalnetwork.com/fish2/aqfm/1999/june/bio/default.asp

[FSOL]

Thanks Randy.

So if I mix a 10:1 ratio of magnesium chloride hexahydrate and Epsom salt, how much more would it be concentrated in Mg compared to the salifert brand I"m using.

Using about 3 tablespoons of the seachem brand increases Mg concentration of 5 gallons of water by 150ppm. My tank has 220g of water, so using 3 tablespoons only increases my Mg concentration by 3.4ppm.

I want to compare so I know if it's worth mixing my own or just buying off the shelf.

[Randy Holmes-Farley]

Depends on how much water you dissolve it into. :D

[FSOL]

Well 220 gallons.

[Randy Holmes-Farley]

No, you asked if the mix would be concentrated. It depends on how much of the 10:1 mix of solids you put into how much mix water (not tank water). You can certainly make magnesium chloride solutions as concentrated as any commercial additive. If you mix Epsom salts into it, you may bet some calcium sulfate precipitate from impurities in the magnesium chloride, but that precipitate is not a big deal.

[FSOL]

Oh I see your point. Well I usually mix lots of that magnesium supplement w/ a half gallon of water. Directions say to mix a small beaker amount w/ one cup of freshwater. But what I usually do is take half a gallon of water and just dump lots of the supplement in it and then in a matter of few hours slowly dump it into the sump. I"m curious if there's a point where if you mix too much Mg supplement w/ the freshwater, it may not do its job properly.

I read in some article you posted that some tanks may have a Mg loss of around 30-70ppm per year. I still have no idea why mine loses about 30ppm in only a week or two.

[Randy Holmes-Farley]

The magnesium supplements are very soluble, so as long as you are not trying for a very concentrated solution, it should be fine.

Demand for magnesium depends on many factors, including what corals you have, the calcification rate, and how you are supplementing calcium and alkalinity.