Magnesium precipitation???

[Joao Cotter]

Hi everybody, and a Happy New Year!

I'm having difficulties in raising magnesium in my tank.
I started with 1200 ppm and wanted to raise to 1350.
I added 300 g of Reef Advantage Magnesium from Seachem and nothing happened. Then I added 940 ml of Kent's Tech M during 3 days. After this I measured Mg and it was 1100 ppm.
I confirmed the results with one other new test kit I bought just for the purpose.
Then I've added for 3 days a complete 1,5 kg pack of Tropic Marin's Bio-Magnesium, which only led me back to 1200 ppm.
As you can see, with all this doses, the dosage recommended by calculators was largely exceeded.
Randy, I've already read your article about magnesium, but I wonder if is there any other special conditions that make magnesium precipitate or deplete so fast in a reef tank.
Coraline hasn't shown a significative increase and I only have 3 small SPS.
Calcium is 370, alcalinity is 8ºdKH and pH is 7.9 or 8.0.
I previously dissolve the magnesium powder additives and add it to the sump.
I'm spending a lot of money in magnesium additives.
I'm thinking on adding more magnesium but I'm affraid it won't raise the Mg concentration.

Thanks in advance

Joao

[Joao Cotter]

Sorry, I forgot to mention my system has 290 gallons.

[spectre9]

Have you tested the Mg levels of a properly mixed batch of saltwater using your preferred salt mix?

Some salts have rather distorted chemistry out of the bag. Oceanic is so close to saturation that anything but pure RO/DI causes precipitation . I discovered this when following Calfo's recommendation of using "pre-buffered water" for mixing salts.

Unless you know that your Mg level is indeed "dropping" I would not consider it a problem.

How old is your tank?

I would get the calcium and pH under control before I worried about Magnesium. Normally there is a 3:1 ratio of callcium to Mg, so I would _expect_ readings of ~1200 unless you raise the Calcium. You are asking for ionic imbalance and pH problems.

-- Patrick

[keeperofthereef]

Magnesium: AKA EPSON SALT's I have been using Epson salts for the last 6 months and have found no ill efects on the tank from it . It is the same composition with the exeption of a litte higher sulphide . It can be bought at your local drug store for about $4.50 for a 2kg bag .
1 gram per liter will raise your levels 100 ppm . Base this on your total tank and sump capacitys 100 gal = 450Liters X 450 grams of epson salts will raise the levels by 100 ppm . Disolve using some tank water in a container you can shake till totaly desolved, I add mine thru the sump . DO NOT INCREASE MORE THAN 100 ppm per day. If your levels 1000ppm increase over 3 Days

[Joao Cotter]

Thank you both.

Last time I tested my salt mix (1.024) it was 1100 ppm Mg.

My tank is only 7 months old.

I was trying to raise magnesium levels because I can't sustain optimal levels of calcium and alk due to CaCO3 precipitation.
pH is not the problem (8.0).

As I read in Randy's article about magnesium, Mg slows CaCO3 precipitation.

Is Epson salts better than the products I'm using? I don't know what are those salts. If I could only translate it to Portuguese, I would find it here.

Anyway, I believe my low magnesium is caused by my salt mix. This doesn't worry me because I'll change for another brand.
The problem I have is how to raise Mg in my tank. Should I insist adding additives or is it possible that something may be causing it to precipitate?

Regards,

Joao

[jfinch]

Joao,

Epsom salt, MgSO4(H2O)7, is ok for a one time adjustment but it does dump quite a bit of sulfate into the the water. A better additive would be 9 parts MgCl2 to 1 part epsom salt. This would keep the sulfate to chloride ratio more in line with seawater. You might have a difficult time finding MgCl2 though.

And I think you should mix the salt(s) up in RO water and dump into the tank. Using tank water could result in MgCO3 precipitation.

[Joao Cotter]

Thanks Jon,
You are talking about Magnesium sulfate and Magnesium chloride.
I don't have any idea where to look for both.
I'll start asking in a pharmacy.
Happy New Year

[keeperofthereef]

Seachem Reef Status
Four kits in one! Tests for magnesium through a titration based procedure in increments of 12.5 mg/L. Tests for carbonate alkalinity, borate alkalintiy and total alkalinity in 0.1 meq/L resolution through a titration based procedure. The kit resolves borate from carbonate and, along with magnesium, this presents a clear picture of the tank`s buffering capacity as well as a very reliable determination of the critical carbonate content required for coral and coraline growth. Each kits can perform 75 determinations for each test.
If you have any questions about the Seachem Reef Status: Magnesium, Carbonate, Borate, Alkalinity

[Muttling]

Randy did a review of SeaChem's borate test kit and found it does a good job with alkalinity, but is unreliable for borate and carbonate. (See link below.)

I use the SeaChem kit for testing magnesium and have been pleased with the results as they are repeatable and seem to provide reasonable results. However, I haven't tried making a magnesium standard and testing the results for known concentrations.

http://www.advancedaquarist.com/issues/june2003/chem.htm

[Randy Holmes-Farley]

Joao:

What magnesium kit are you using?
Maybe it is not working well.

I don't think it likely that you are precipitating large amounts of magneisum solids from the tank on a time scale of 100+ ppm over a few days.

This article describes magnesium in more detail:

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

[keeperofthereef]

No i do not , I was just stating not to exceed The " MAXIMUM" suggested dose or some one might try to do it all in one application ! I have seen tanks with readings of 850ppm and just supplied the imformation to warn against overdosing !

[fish100]

Are you using a sand bed? I had a problem with low Mg and a lot of my sand also clumped, hard as a rock some of it. I was also using Tropic Marin (not that that is of necessary importance).

I did eventually get the Mg and Ca up respectively.

[keeperofthereef]

I removed my sandbed about 2 months ago and have found less swings in all of the parameters , my skimmer only removes half the amount since i have done this .

[Joao Cotter]

What magnesium kit are you using?
I'm using 2 magnesium test kits:
- JBL (gives Mg + Ca; for Ca I use Salifert);
- Elos (only Mg; it's an Italian brand)

Both give me the same results.

was just stating not to exceed The " MAXIMUM" suggested dose or some one might try to do it all in one application !
I'm far from exceeding maximum dosage. I dose in 3 days.
Are you using a sand bed?
Only in my refugium. My tank has a bare bottom.
Do you think the sand bed in my refugium is causing some problems?

Thank you all

Joao

[Randy Holmes-Farley]

I'm far from exceeding maximum dosage. I dose in 3 days.

That's OK. Recommended dosages are for maintenance, not for correcting low levels.

No, I do not believe that sand can cause low magnesium problems.