# Soft Water



## gunny bedford (13 Feb 2022)

Hi
I live down on the Kent coast near Folkestone, the water is very hard is this area. Ive wanted to use soft water in my tank for some time, but never got round to purchasing a water softener. Luckily we treated ourselves to a hot tub In December and this particular type uses soft water, it came with a  very large resin exchange ? (put salt in it) water softener that can soften the 1500 odd liters in the tub. It does a good job and the water is very soft in the tub, so happy days i thought i can finally get a soft water tank ! However I am aware that softened water needs to have additives for use in a tank, but not sure which one's are best ? Ideally i would like to use a "one does all " type if they exist ? or do you have to use various ones to get the chemistry right ? I would like to try an amazon style tank with tetra's etc. in it, perhaps going to Discus when it has been established for a while, so any assistance in what i would have to add to freshly softened water would be greatly received, thanks Neil


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## hypnogogia (13 Feb 2022)

You shouldn’t  use water softener water.  It essentially replaces the calcium and magnesium ions with sodium ions, which is not healthy for fish.  If you want soft water, you’ll need to use Reverse Osmosis water that you then remineralise. 

How hard is your water? What KH and GH values do you have?


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## gunny bedford (13 Feb 2022)

Hi my KH is 14, I'm using a tetra test kit, for some reason the GH test is not functioning correctly ? its been some time since i tested, can the chemicals break down ? when i first got the test kit i recall the GH was 16 and the water would turn from Red to Green as per the instructions, but now when i test it just stays a light green/yellow colour ?? But im guessing as my KH is 14 my GH should be fairly high as well ? i will purchase a new kit today and see what that says.


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## dw1305 (13 Feb 2022)

Hi all, 


gunny bedford said:


> came with a very large resin exchange ? (put salt in it) water softener that can soften the 1500 odd liters in the tub.


You will probably find you get <"through a lot of salt">. 


hypnogogia said:


> You shouldn’t use water softener water.


That is the one, the Lenntech document <"Ion exchange for dummies"> is really useful .  

The water is soft in terms of dGH, because you have exchanged each calcium (Ca++) ion for  two sodium (Na+) ions, but it has the same dKH. 

This is because it is <"strong acid cation exchange"> exchange and the anion remains the same, so now you have Na+ HCO3+, and sodium carbonate / bicarbonate (Na2CO3 / NaHCO3) and calcium chloride (CaCl2) and both of these <"compounds are soluble">.

cheers Darrel


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## gunny bedford (13 Feb 2022)

Here is a report from my water supplier


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## Oldguy (13 Feb 2022)

gunny bedford said:


> I live down on the Kent coast near Folkestone, the water is very hard is this area. Ive wanted to use soft water in my tank for some time


As above sodium ions from the water softer are not really suitable for fish keeping.
Depending on your circumstances why not collect rain water, it comes for free, and mix it with your tap water to get the hardness/softness that you want.  Assuming that you total harness is 300pmm, then 50:50 rain water to tap water would yield a total harness of 150ppm. (1ppm is mg/litre) and so on pro rota.

If you are metered it might save you a little money too.


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## dw1305 (13 Feb 2022)

Hi all,


Oldguy said:


> Depending on your circumstances why not collect rain water, it comes for free, and mix it with your tap water to get the hardness/softness that you want. Assuming that you total harness is 300pmm, then 50:50 rain water to tap water would yield a total harness of 150ppm. (1ppm is mg/litre) and so on pro rota.
> 
> If you are metered it might save you a little money too.


I have <"very similar tap water"> to @gunny bedford . I'm also a <"rain-water user">, and I would highly recommend it.


gunny bedford said:


> Hi my KH is 14, I'm using a tetra test kit, ............ Here is a report from my water supplier.


Perfect. You can assume that nearly all the hardness comes from the <"chalk (CaCO3)">, which supplies approx. <"1 : 1 dGH and dKH">.   You can tell it is chalk aquifer water by the very similar minimum, mean and maximum values for alkalinity, calcium (Ca)  etc.

The maths to work them out from your water report is <"relatively straight forward">, you divide "Hardness Total" figure of 293 by 17.86 (the definition of 1 dGH) which gives 16.4, that is your dGH.  If you multiply the "total hardness" figure by 40% (the percentage of calcium in CaCO3) you get the 117 mg/l (ppm) Ca figure.

For dKH you divide the "Alkalinity" = 320 by 17.86 to give you 17.9 dKH. 


dw1305 said:


> The 17dKH was for Corsham where I live, but it will be a similar value for all of the water that comes from a chalk or limestone aquifer, so most of the S. and E. of England. It is back to the equilibrium value for the CO2 ~ carbonate buffering system.


I didn't actually need to do the maths, because all hard water in the S. of the UK is pretty similar and about 17dGH / 17dKH.

cheers Darrel


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## gunny bedford (13 Feb 2022)

thanks all for the explanation, so then assuming my water softener with the hot tub is useless for aquarium use (Gutted LOL) apart from rainwater what softener would people recommend ? i have a small room attached to the garage which when first built i think was supposed to be a utility area for washing machine etc, but is currently used to store my bikes ! but it does have hot and cold water supply and power so could perhaps install something there ?


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## hypnogogia (13 Feb 2022)

gunny bedford said:


> thanks all for the explanation, so then assuming my water softener with the hot tub is useless for aquarium use (Gutted LOL) apart from rainwater what softener would people recommend ? i have a small room attached to the garage which when first built i think was supposed to be a utility area for washing machine etc, but is currently used to store my bikes ! but it does have hot and cold water supply and power so could perhaps install something there ?


You could make your own RO water (very wasteful) or use KCL (potassium chloride) instead of NaCL (salt) in a water softener.  That way the magnesium and calcium ions are exchanged for potassium ions, which are a part of macro plant fertiliser anyway.  You could also buy RO water from Spotless water at about 3.5p per liter.

Easiest, cheapest and environmentally friendliest is to use rainwater.


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## dw1305 (13 Feb 2022)

Hi all, 


gunny bedford said:


> but it does have hot and cold water supply and power so could perhaps install something there ?


You could install a RO (Reverse Osmosis) unit. As @hypnogogia says there are some issues with these, but a lot of people use them. @ian_m might be your best bet <"for some advice">.

cheers Darrel


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## ian_m (14 Feb 2022)

As pointed out some people are using potassium chloride instead of normal salt (sodium chloride) to produce whole house soft water that CAN be used in a fish tank. In fact the potassium is highly beneficial  in planted tank. BUT I get 8kg of salt for £4 and cheapest I found potassium chloride was £20 for 8kg. Also as potassium is "heavier" than sodium (atom wise) so you get less softening capability per gram with potassium chloride than sodium chloride, making potassium even more expensive.

So you really need to consider, why do you require soft water, fish/plants generally don't care about water hardness. Water consistency is often better, as it is very easy to just work with the water you have "on tap".

So if you insist soft water is the way to go then RO units and/or Spotless water is the way to go, along with associated water wastage and cost.


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