Water Hardness Units?

[Bigman]

Hi all, 
 
Just been reading up on water hardness and I'm a little puzzled over units....
Some fish profiles state a required water hardness in 'dGH', others are either 'H; 'N' or ppm
 
Are they all the same?
 
For examples: 
 
Zebra Danios
Temperature: 18 to 24 C - pH: 6.5 to 7.0 - Hardness: 5 to 12 dGH
 
Pygmy Corydoras
Temperature: 22 to 26°C - pH: 6.4 to 7.4 - Hardness: 2 to 15 H
 
Harlequin Rasboras
Temperature: 22 to 25°C - pH: 5.0 to 7.0 - Hardness: 1 to 10 N
 
Sword tails
Temperature: 21 to 28°C - pH: 7.0 to 8.0 - Hardness: 12 to 18 N
 
Siamese algae eaters
Temperature: 22 to 26°C - pH: 6.0 to 7.5 - Hardness: 18 to 268 ppm
 
 
I live in a very 'hard water' area, so I was just checking whether or not the above fish would be ok? (in a community tank).
 
Regards
Tony 

 

[JonesyJ666]

how do you get water hardness level lower?

 

[Bigman]

Hi JonesyJ666,
 
I'm a newbie to fish keeping so I'm still learning.... but from what I have read, you can use a domestic type water softener, or purchase water from your LFS which has gone through an RO unit. but in some areas, (prominently Midlands and north UK) the tap water is already soft. In my area, the tap water comes from chalk hills. and therefore is very hard.
 
Hardness is a measure of Calcium ions within the water itself, when you soften water, you either replace the Calcium ions with Sodium ions (domestic water softening) (base exchange method it's called) or remove them completely by microscopic filtering (Reverse Osmosis - RO) method......
 
All this science just to keep fish..... fascinating eh?
 
Regards
Tony

 

[TwoTankAmin]

1dgH = 17.8 ppm for both GH and KH.
 
Never seen N.
 

 
General hardness (GH) refers to the dissolved concentration of magnesium and calcium ions. When fish are said to prefer ``soft'' or ``hard'' water, it is GH (not KH) that is being referred to. Water hardness follows the following guidelines. The unit dH means ``degree hardness'', while ppm means ``parts per million'', which is roughly equivalent to mg/L in water. 1 unit dH equals 17.8 ppm CaCO3. Most test kits give the hardness in units of CaCO3; this means the hardness is equivalent to that much CaCO3 in water but does not mean it actually came from CaCO3.
 
KH or alkalinity aka buffering capacity refers to water's ability to keep the pH stable as acids or bases are added. In freshwater aquariums, most of water's buffering capacity is due to carbonates and bicarbonates. KH doesn't affect fish directly, so there is no need to match fish species to a particular KH.

from http/fins.actwin.com/aquariafaq.html

 

[daizeUK]

I believe if you click on 'Calculator' at the top of the page it will do conversions for you.
 
You can either buy test kits to check your exact water hardness or just check your local water supplier website and they will usually tell you how hard (e.g. my water board says I have 300 mg/L CaCO3 and my test strip are reading 15-18 dGH, either way it's pretty hard

)
 
pH is usually (but not always) linked to hardness.  Hard water is usually alkaline e.g. mine is 8.2 so I use that as a rough guide, any fish that prefers acidic waters is out unless it is noted as being especially hardy or adaptable.  But different sites will tell you different things for the same fish so it's hard to tell which are suitable.
 
Swordtails will definitely be fine though, they love hard water!

 

[Bigman]

Thanks TwoTanksAmin, DaizeUK....
 
I can remember doing this at school, many moons ago  but I'm afraid the old grey matter needs a prod every now and again these days.....
 
My locai water Authority gives the following figures for Hardness and Alkalinity
 
                                            Min     Mean     Max
Hardness, Total(mg/l Ca)    116     120.5     132.2
Alkalinity (CaCO3)(mg/l)      270.1  281.5     291.8
 
I note the units are mg/l, so can I take this as the same as ppm?
 
Regards
Tony

 

[Essjay]

They are so close as to be the same thing for our purposes.
 
My water company used to give the alkalinity, and the mean value was almost exactly the same as my KH as measured by an API tester.
 
 
 
As for using a domestic water softener to reduce the hardness, be careful. If it's the type that replaces calcium with sodium, you shouldn't use it. That water still contains a lot of dissolved minerals but not the kind the most fish have evolved to cope with.

 

[Bigman]

Thanks for that essjay, much appreciated.
 
And thanks for putting me right about the domestic water softener too..... I was in fact thinking about the type that replaces calcium with Sodium... so I will now leave that well alone.
 
I guess I'm down to using API Proper pH 7.0 then eh?
 
Regards
Tony

 

[daizeUK]

I wouldn't mess with your pH, leave it alone.  Like I said, I have much harder water than you at 300 mg/L and I don't try to alter it.  You will do fine with sensible stocking choices.
 
If you really must keep soft-water loving fish then it's better to mix your tap water with RO or rain water.

 

[Bigman]

Thanks daizeUK,
 
Much appreciated.....
 
Tony