Tropical Fish Keeping - Aquarium fish care and resources

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Tycoon 05-30-2007 01:21 AM

Hard and Soft water
I sometimes hear and read about different fish prefers either hard or soft water...

What is hard and soft water? Can someone explain it to me in a simple way?

ttmmm2001 05-30-2007 01:39 AM

This is true. Certian fish prefer water with different qualities than other fish.

Do some research on the fish you are interested in and find out what water types they prefer.

Then go to a pet store and buy a 5 in 1 water test. They will be little strips in a bottle and give instructions on how to use them. It will tell you the Hardness (Gh) and Ph of your water.

Dont worry if your water comes up on the top or bottom of any of these tests. It doesnt mean your water is "Bad", thats just the type of water you have in your area.

Use the results of your test to find fish that match your water type and they will be very happy. A little bit of a mis-match usually isnt a problem with most common fish types. Just do some research on your fish to find out =)

Hope that helps you out.

GW 05-30-2007 05:45 AM

Alkalinity (Carbonate Hardness-KH) measures dissolved bicarbonate and carbonate ions. They are commonly referred to as the buffering capacity. KH determines on how stable your pH will be and is therefore very important.

General Hardness (GH)
GH primarily measures calcium and magnesium ions.

This link may help you understand...

Falina 05-30-2007 07:56 AM


Then go to a pet store and buy a 5 in 1 water test. They will be little strips in a bottle and give instructions on how to use them. It will tell you the Hardness (Gh) and Ph of your water.
I recommend the liquid tests as the strips tend to be very inaccurate.

leslie123 05-30-2007 12:32 PM

So these values would mean ...
I hope it's okay if I add my question to this topic? It relates perfectly.

So if my values are:

KH (Carbonate) = 8-9
DH (General) = 0-1

Then do I have ... very soft water with a good buffering capacity? Or do I have hard water? What KH would be consdidered good buffering?

Thanks!! (And I DO apoligize if I shouldn't be posting this here, but should post a new topic. Please let me know!)


fish_4_all 05-30-2007 01:33 PM

Hard water would be a GH of about 14, normally you want to keep it somewhere around 4-8. The numbers are not set in stone and many sources give different numbers but it all comes down to your fish as to what you want the numbers to be. Most fish are fine in a range of both KH and GH where certain ones will need harder or softer water.

You never want to see your KH below 3 because of the buffering capacity and I think the GH needs to stay around 3-5 to give the calcium and magnesium needed for good health. It has to do with something, the GH does, as far as osmotic pressure and swim blatters but I don't know the technical aspects of it.

GW 05-30-2007 01:50 PM

Leslie, If I've done my calculations correctly to convert over to PPM:

You have "Soft" water according to your (GH)General Hardness of 0-1.
Your (KH)Carbonate Hardness level, also known as "Alkalinity", should buffer the PH level(acidity/alkalinity) preventing quick swings which could be fatal to your fish. I'm getting a conversion to PPM of approx. 160 PPM for your KH level.

fish_4_all 05-30-2007 02:04 PM

Thats about right but there is one problem when converting. It depends on the test kit you have. I have seen it where it can 16:1 ppm:degrees and I have seen it as low as 10:1 ppm:degrees. Mine is 16:1 and a friends is 10:1. I guess there is one out there that is 23:1 but I haven't seen it yet.

The conversion should be in your instructions for the test kit though so it should be easy to do.

Tycoon 05-30-2007 05:11 PM

I have one more question guys... tap water is generally hard water right?

I plan on buying some guppies and platies when i get my very first tank ever and i think they prefer hardy water.

fish_4_all 05-30-2007 05:16 PM

My tap water is extremely soft! Zero KH and GH. I have to add crushed coral to my tanks to keep it up high enough just for the fish. I also add calcium citrate to the tanks just to make sure as well as MgSO4 (Epson Salt) Tap water is different everywhere you go. I would bet my tap water on the East side Of Washington was extremely hard but it was from a well in the desert.

The only way to know for sure is to test your tap water after you have left it out for 24 hours. Either that or try to get a city water works employee to return a phone call which took me almost 6 months.

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