Can the addition of Mag or Calcium Chloride supplemments raise SG?

AcroporAddict

There is no substitute.
Can dosing a magnesium chloride or calcium chloride supplement have the effect, even if only slightly, of raising the specific gravity of saltwater?
 

ReefCowboy

New member
I had posted a thread about the same topic a few days ago, my salinity went from 1.027 to 1.030 since i started dosing more of the two part supplement(i used b ionic). It seems that after calcium and alkalinity are consumed, the end solution is salt, thus raising salinity. Sorry im not stating the exact compounds, i took chemistry a long time ago, but maybe someone can chime in in more technical words :)
I found out my salinity was high over the weekend, and am now working on getting the sg down with more diluted wc's...
 

AcroporAddict

There is no substitute.
I had posted a thread about the same topic a few days ago, my salinity went from 1.027 to 1.030 since i started dosing more of the two part supplement(i used b ionic). It seems that after calcium and alkalinity are consumed, the end solution is salt, thus raising salinity. Sorry im not stating the exact compounds, i took chemistry a long time ago, but maybe someone can chime in in more technical words :)
I found out my salinity was high over the weekend, and am now working on getting the sg down with more diluted wc's...

I do magnesium corrections with Randy's 2 part occasionally, and I see my SG go from 1.025 to 1.026. This is adding about a gallon of 2 part to a total system volume of 465 gallons or so. You end up adding so much magnesium because so much of magnesium chloride hexahydrate is water. I have always assumed it is the chloride ion that adds to the SG, whether the chloride ion is from magnesium chloride or calcium chloride.

A guy on my local reef club website is asking why his SG is fluctuating (outside of water changes), and one guy posted categorically that the only way that SG will fluctuate is either by the addition or removal or addition of fresh water through evaporation or makeup water. I wanted to add that mag chloride or calcium chloride can raise SG, but wanted to confirm it here before posting.
 
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thegrun

Team RC
Specific gravity indicates density, while salinity refers to the actual weight of the salt in the water sample. The density of the water is effected by the addition of any salt or mineral to the sample.
 

dkeller_nc

New member
Specific gravity indicates density, while salinity refers to the actual weight of the salt in the water sample. The density of the water is effected by the addition of any salt or mineral to the sample.

Or any other dissolved substance (doesn't have to be an ionizable salt). The guy that posted "categorically" is either confusing conductivity with specific gravity, or doesn't understand chemistry.
 

wayne in norway

New member
Yes, adding lots of 2 part/3 part can leave you with a high salinity with left over Na and Cl ions. There are calculators around that will work out where daily dosing would leave you after 6 months.

Now you can fix that by removing some saltwater and replacing it with RO. However all you've added is Na and Cl and seawater is more than that, so your solution will trend towards a boring brine. Balling , balling light, Triton et al try to fix this by adding trace elements, but Balling lite also recommend 10% water changes to stop the overall chemistry getting out of whack
 

bertoni

Premium Member
The simple answer is that magnesium chloride and calcium chloride both will raise the SG, although the amount generally is too small to measure for any single dose. A 2-part can raise the SG quite a bit over time, maybe 0.001 SG units in a month.
 
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