# Adding Magnesium (epsom salts) to my hard water



## tommyleestaples (10 Feb 2010)

I have hard water GH of 19 dgh and KH of 13 dkh. 

If I add magnesium (epsom salts) to the water will it make it harder?


----------



## Dave Spencer (11 Feb 2010)

Do you know for sure that your tap water is low on Mg? With a GH of 19, there should most likely be a fair amount of Mg present, although it is possible for it to be low. Adding Mg will increase the GH.

Dave.


----------



## tommyleestaples (11 Feb 2010)

Its just its something ive been told by a planted tank keeper near my area.


----------



## a1Matt (11 Feb 2010)

GH is made up of calcium and magnesium.
But it could be in any ratio.

With a GH as high as yours I agree with Dave and suspect you have enough of both, but that is only an educated guess.

My tap has a lot more Mg than Ca (GH of 10) so I add calcium (in the form of gypsum).


----------



## dw1305 (11 Feb 2010)

Hi all,
It will add to the GH and conductivity (TDS), but not to the KH as that is a measure of the carbonate content, and "Epsom Salts" are "magnesium sulphate heptahydrate". 





> My tap has a lot more Mg than Ca (GH of 10) so I add calcium (in the form of gypsum).


 this is an interesting one, have you got the figures for Mg & Ca? our chalk aquifer water has a huge amount of calcium but hardly any magnesium (and this would be the similar situation across most of S. England).

cheers Darrel


----------



## dw1305 (11 Feb 2010)

Hi all,
Should also have said that "James C's" sticky is an excellent summary of GH/KH <http://www.ukaps.org/forum/viewtopic.php?f=51&t=4869&start=0>, and that the magnesium raises GH because the Epsom salts disassociate to a multivalent cation, Mg++.
cheers Darrel


----------



## tommyleestaples (11 Feb 2010)

So you would recommended adding Magnesium to my water? Maybe 10 ppm?


----------



## a1Matt (11 Feb 2010)

dw1305 said:
			
		

> > My tap has a lot more Mg than Ca (GH of 10) so I add calcium (in the form of gypsum).
> 
> 
> this is an interesting one, have you got the figures for Mg & Ca? our chalk aquifer water has a huge amount of calcium but hardly any magnesium (and this would be the similar situation across most of S. England).
> ...



I typed my post in a hurry, I should have said that I suspect I have low Ca in my tap water.
It was an anecdotal correlation based on the fact that my balansae show calcium deficiencies (and no magnesium deficiencies) and then showed improved growth after dosing calcium.



			
				tommyleestaples said:
			
		

> So you would recommended adding Magnesium to my water? Maybe 10 ppm?



If it was me I would add some and if there was no improvement in plant growth after 3 weeks stop adding it.  If you are using the EI method of regular water changes then any excess will be removed.


----------



## tommyleestaples (11 Feb 2010)

I have not planted the plants yet so maybe a good idea would be to plant the plants and see if I get any signs of magnesium defiancy then I can start adding the Magnesium (Epsom Salts)


----------



## a1Matt (11 Feb 2010)

tommyleestaples said:
			
		

> I have not planted the plants yet so maybe a good idea would be to plant the plants and see if I get any signs of magnesium defiancy then I can start adding the Magnesium (Epsom Salts)



That would work


----------



## Stickleback (11 Feb 2010)

I found this thread interesting:

viewtopic.php?f=11&t=526&start=0&hilit=

Especially as I live in SE London, where apparently we have a high GH but low magnesium. Because of this I started dosing recently and although it is only early days it does seem to be helping.

Don't know whether you saw this, but shows how important magnesium is.

viewtopic.php?f=24&t=9804

R


----------



## dw1305 (11 Feb 2010)

Hi all,
If you already have the Epsom Salts, I'd add a small amount (you only need to add 2-3 ppm), as it won't do any harm and if your water is Mg deficient it will provide enough Mg. For many terrestrial plants the problems occur when the Ca/Mg ratio becomes very large and this causes leaf chlorosis in Azaleas, Citrus etc. Magnesium is mobile within the plant which gives the instant effect in the post Rufus highlighted.
cheers Darrel


----------

