Magnesium

[ufans]

I finally got a Mg test kit from Seachem and to much of my amazement my Mg was way low. I have had some moderate pH problems in the past that I had attributed to excess CO2 but I wonder if Mg might also be a contributing factor.

I would like to know what are the typical reading for Mg in a tank that has never supplemented with Mg because my Mg level was <125 ppm and I ran the test several times. Is it possible to be that low or might I be doing something wrong?

I am running 75gal (~110gal total volume) mixed reef with mostly softies. The tank is about 10months old and had high ALK for most of the beginning months trying to keep the pH > 7.8. The tank is quite stable now. I dose Kalk on a regular basis in order to maintain Alk & Ca within the ideal ranges.

Thanks
UFANS

[Randy Holmes-Farley]

I finally got a Mg test kit from Seachem and to much of my amazement my Mg was way low. I have had some moderate pH problems in the past that I had attributed to excess CO2 but I wonder if Mg might also be a contributing factor.

I do not believe that magnesium contributes significantly to pH problems. Low magneisum is more likely to cause difficulty maintaining adequate calcium and alkalinity, even with substantial additions.

<125 ppm Mg++ is likely an error. Magnesium ought to be about 1300 ppm, and is rarely below 600 ppm.

What kit? Did you measure your salt mix? What mix?

These articles may help:

Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm

Magnesium and Strontium in Limewater
http://www.advancedaquarist.com/issues/dec2003/chem.htm

[sjvl51]

Maybe have your water tested by another reefer.

Vickie

[ufans]

Yep. You are correct. I was interpreting the results wrong. I was using SeaChem's Reef Status Mg test kit and though that the mL reading I was suppose to take was how much titrant was left vice how much titrant was used. Quite a difference in results ;)

The reason I though it might impact pH was that I was under the belief that a high Alk (>5.8meq/L) could cause Mg to percipitate and thus I might have lost some of my Mg saturation in my water. The same goes with Ca.

Everything looks great. All parameters within ideal ranges. Finally.

BTW. I wrestled with low pH problems for a long time and after 4-5 months of using airline tubing to pump outside air into my skimmer and sump I believe I have enough evidence to argue that it is a reasonable way to efficiently cope with a high-efficiency house that has elevated CO2 problems. It isn't the total solution, but after weeks of doing it I rarely see my pH fall below 7.9 even if my Alk falls near 2meq/L.

Thanks again for all the help.
Happy Reefing
UFANS

[Randy Holmes-Farley]

I was interpreting the results wrong.

All's well that ends well. :)

It isn't the total solution, but after weeks of doing it I rarely see my pH fall below 7.9 even if my Alk falls near 2meq/L.

That's good to hear!

Happy reefing. :)

[willis]

Randy, not to hijack this thread but is a reading of 1200 (Mg) too low. I have a 300 gallon (475 gal. total system).
Are there othere things that can help raise the mag. levels in our system. Buying additives gets expensive.

[Randy Holmes-Farley]

It is borderline. I'd raise it to 1300 ppm with a commercial supplement, or in this case of a smasll one time correction, perhaps just Epsom salts from a drug store.

This calculator will help:

http://home.comcast.net/~jdieck1/chem_calc3.html

[birdman204]

coolest calculator ever. ;)
I have a question about using epsom salts to raise Magnesium.
wouldn't this raise the Salinity of the aquarium if added? Also, regarding raising the magnesium of artificial seawater used for Water changes, how would one do this with the use of epsom salts? Is there another way aside from commercially sold products?

[ufans]

Epsom Salts = MgSO4 = Magnesium Sulfate

It really isn't salt. I figure they just named it that because it looks like it. There isn't a risk of raising salinity, just sulfate. If the Mg is really low then something without Sulfate is recommended.... like Magnesium Chloride (MgCl2).

I have learned more about chemistry from working on my reef tank than I ever did in school.

[Randy Holmes-Farley]

The rise in salinity is very minor and easy to correct for. The rise in sulfate from using Epsom salts is harder to deal with,and is why I don't recommend it as a regular addition unless you are using calcium chloride for all calcium additions (see home made two part link below).

If you can find a high quality magnesium chloride, then youcan maked your own additive (see link below), but that is not easy to find.

These articles may help:

Magnesium
http://www.advancedaquarist.com/issues/oct2003/chem.htm

Magnesium and Strontium in Limewater
http://www.advancedaquarist.com/issues/dec2003/chem.htm

A Homemade Magnesium Supplement
http://web.archive.org/web/20030624220704/http://www.animalnetwork.com/fish2/aqfm/1999/june/bio/default.asp

A Homemade Two-Part Calcium and Alkalinity Additive System
http://www.advancedaquarist.com/issues/april2004/chem.htm


from the first one:

"Supplements for Magnesium in Marine Aquaria

There are a variety of commercial supplements for magnesium. Those supplements made by ESV, Seachem, and Kent are quite popular, although I’ve not seen any detailed analyses of them. Assuming they are what they claim to be, they are fine products to use, even for large increases in magnesium. I’ve used the ESV supplement, along with ones that I’ve made myself.

One thing to keep in mind about magnesium supplements is that they are all necessarily quite “dilute� even when presented as dry solids. The reason for this is that magnesium is a doubly charged and very light ion. So in a salt form, or when dissolved in a liquid, it is necessarily attended by a large number of quite heavy counterions (chloride and sulfate, especially). Commercial dry supplements may be only 8% magnesium by weight, for example.

Compounding the issue is the simple fact that there is so much magnesium in an aquarium that significant supplementation requires a great deal of material. A 100-gallon aquarium contains about a pound of magnesium! In order to raise that same aquarium by 200 ppm of magnesium, one would need to add on the order of 2 pounds of dry magnesium salts!

Epsom Salts (USP grade magnesium sulfate heptahydrate) is readily available in drug stores and very inexpensive. The problem is that if you were to raise magnesium by a large amount (or a small amount several times) the aquarium water will become relatively enriched in sulfate. This enrichment may not be a problem for some aquaria, especially those using salt mixes already deficient in sulfate, or those that experience frequent water changes. Bingman has addressed these enrichment issues and has suggested a recipe for home made supplements based on Epsom Salts and magnesium chloride. The problem is in getting the latter in adequate purity.

As an alternative, some aquarists have begun to use Nigari, a Japanese product that is derived from seawater and is used to manufacture tofu. It appears to be mostly magnesium salts of chloride and sulfate, but how much sulfate and how much chloride, as well as what other metals remains to be demonstrated.

Whatever supplement you choose, I’d suggest targeting the natural seawater concentration: 1285 ppm. For practical purposes, 1250-1350 ppm is fine. I would not suggest raising magnesium by more than 100 ppm per day. If you need to raise it by several hundred ppm, splitting the addition over several days will allow you to better home in on the target concentration, and might possibly allow the aquarium to deal with impurities that may come in with the supplement.

It has been suggested that adding dolomite to CaCO3/CO2 reactors can help with magnesium problems. Dolomite is a material that contains both magnesium and calcium carbonate. If dolomite is being added to the reactor to maintain existing appropriate magnesium levels against the continual depletion via calcification (for example, if the calcium carbonate being used is too low in magnesium to maintain adequate magnesium) then this is a fine approach.

However, this method is unsuitable if the goal is to raise magnesium levels. The problem is that for every magnesium ion released from the dolomite, 2 units of alkalinity are also released:

MgCO3 ---> Mg++ + CO3--

Consequently, if one wants to raise magnesium by 100 ppm, the alkalinity will necessarily rise by 8.2 meq/L (23 dKH). The only way around this problem is to add a mineral acid (not vinegar) to the aquarium to reduce the alkalinity, and that may be more problematic than just adding magnesium in the first place."

[birdman204]

Originally posted by ufans
Epsom Salts = MgSO4 = Magnesium Sulfate

Somehow I knew this, and yet, My brain still managed to ask well after my bedtime :P Thanks for the link Randy , I bookmarked it last night while peering through another thread.
I like the note on Dolomite. Thanks

Would this be a good source? Is there anything I am looking for different. The iron oxide in this product shouldn't be problematic correct?

http://www.imascominerals.com/pdf/minerals/Dolomite-Creston.pdf

[Randy Holmes-Farley]

I think the particles are probably too small for a reactor. That 325 mesh is quite a fine powder.