Reef Chemistry Question of the Day #186 Magnesium Supplements

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
66,553
Reaction score
62,861
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
Reef Chemistry Question of the Day [HASHTAG]#186[/HASHTAG]

There are a variety of dry materials that are suitable for supplementing magnesium to a reef aquarium, and while all are necessarily much less than half magnesium by weight, they vary in potency.

Rank order the following possible additives from most potent to least potent in terms of magnesium per unit weight.

A. Magnesium sulfate (anhydrous)
B. Magnesium sulfate heptahydrate (Epsom Salt)
C Magnesium chloride (anhydrous)
D. Magnesium chloride hexahydrate (Mag Flake)

So a suitable form of the answer is something like

A>B>C>D

Good luck!























.
 

JimWelsh

Valuable Member
View Badges
Joined
Nov 5, 2011
Messages
1,547
Reaction score
1,679
Location
Angwin, CA
Rating - 0%
0   0   0
What ^^^ he said. C>A>D>B. Even though there are two chloride ions in MgCl2 vs. the one sulfate ion in MgSO4, sulfate is more than twice as heavy as chloride, so MgCl2 is still lighter than MgSO4. That extra water molecule just reinforces this sort order for the hydrated version of the salts.
 

beaslbob

2500 Club Member
View Badges
Joined
May 11, 2009
Messages
4,086
Reaction score
960
Location
huntsville, al
Rating - 0%
0   0   0
under that assumption most potent is the greater percentage of magnesium

sulfate is heavier than chloride even with 2 chlorides.
the hydrate water down the mess

so the first two would be the anahydrous

chloride first then the sulfate

c>a

the waters vary but the chloride and 6 waters is less the the sulfate and 7 waters

so
d>b

total
c>a>d>b

which agrees with taylor.

even more amazing is anyone agreed with me.

:p
 

beaslbob

2500 Club Member
View Badges
Joined
May 11, 2009
Messages
4,086
Reaction score
960
Location
huntsville, al
Rating - 0%
0   0   0
just to make it difficult:

atomic mass magnesium chloride oxygen hydrogen sulfur
__________24.305___ 35.45___5.999_1.0008__ 32.06

water_h20___18.0006
sulfate_so4___96.056
______________________magnesium_chloride_ sulfate__water__total______mag___ percent
magnesium sulfate anahydrous___1________0______1_____0____120.361__ 24.305____20.19342%
magnesium sulfate heptahydrate__1________0_______1____7____246.3652__24.305____9.86544%
magnesium chloride anahydrous__1________2______0_____0____95.205___24.305 ___25.52912%
magnesium chloride hexahydrate_1_________2______0_____6___203.2086__24.305____11.96062%

Now I forgot which one was abcd.

I guess they in the same order as the question.

so C>A>D>B
 

coralcruze

Well-Known Member
View Badges
Joined
Sep 25, 2014
Messages
902
Reaction score
254
Rating - 0%
0   0   0
tagging along and have a question.

can we also include actual product sources where one can buy these? I currently use 100% Epsom salt purchased at local CVS. Its probably the least potent but that's from practical experience and nothing else.
 

Piranhapat

Active Member
View Badges
Joined
Jan 1, 2014
Messages
439
Reaction score
206
Location
Westchester
Rating - 0%
0   0   0
I just picked up TLF of Magnesium pronto dry power at a very good price. 500g can make about 50 gals of magnesium at 12.5. Better than paying ESV $25 for a gal.
 
OP
OP
Randy Holmes-Farley

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
66,553
Reaction score
62,861
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
tagging along and have a question.

can we also include actual product sources where one can buy these? I currently use 100% Epsom salt purchased at local CVS. Its probably the least potent but that's from practical experience and nothing else.

That's a fine choice, and I've used it.

If you can find Mag Flake (big bags for snow melting) that is seemingly fine. I've used that too. But more readily available is magnesium chloride hexahydrate from BRS, Dr Foster and Smith, etc.
 

Cory

More than 25 years reefing
View Badges
Joined
Oct 30, 2014
Messages
6,882
Reaction score
3,129
Location
Canada
Rating - 0%
0   0   0
Mag chloride without water is the most potent addition of mag.
 
OP
OP
Randy Holmes-Farley

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
66,553
Reaction score
62,861
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
And the answer is... C>A>D>B

Good job!

Others have done the calculations, so I won't bother.

One remarkable thing is how low they all are in potency. There's just no way around the fact that combining a light ion like magnesium with any suitable (and heavy) elements to use as an additive makes it weak.

Happy Reefing. :)
 
Back
Top