GH or KH? What tells what about hard water?

eduh

Guys,

I have been reading about it and I can’t clearly understand the hard/soft water stuff.

I read the article pinned in this forum about pH, KH and GH, how KH stabilise PH, and GH measure the other minerals.

But I also read that hard water have high KH and GH.
Or if from tap water I can have hard water with High GH but low KH.

Well, I am really confused. I tested my tank water and I got:

4dKH
pH: 7.6

Do I need to test my GH to determine my water hardness? If yes, I will buy the liquid test for it.

Or low KH means soft water?

I appreciate if someone could confirm how you confirm the water hardness.
 

michaelsf90

If your ph from the tap is 7.6 you have hard water. Leave the water from the tap in a cup for 24 hours and test again. That will give you a better reading as all the carbon dioxide will have evaporated. Gh tends to be higher for hard water. The kh is what acts a buffer to keep your ph stable. So if you have low kh your ph over time will go down I think. You need some carbonate hardness and regular water changes to keep your ph from swinging and changing. I hope that helps
 
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eduh

If your ph from the tap is 7.6 you have hard water. Leave the water from the tap in a cup for 24 hours and test again. That will give you a better reading as all the carbon dioxide will have evaporated. Gh tends to be higher for hard water. The kh is what acts a buffer to keep your ph stable. So if you have low kh your ph over time will go down I think. You need some carbonate hardness and regular water changes to keep your ph from swinging and changing. I hope that helps

Thank you. I checked my source parameters on its official website and they have pH at 7.6. But I will test it anyway.

I do weekly WC from 30 to 50% depending on how dirty is the gravel.
 
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michaelsf90

I'd say your fine with that ph. Just test regularly to make sure it isn't dropping. Where I live its very soft water. Little general and carbonate hardness. Over months my ph dropped even with water changes. Having no kh meant their was no buffering whatsoever so it just kept going down. I had to put crushed coral in to naturally raise the hardness. The crushed coral dissolves any acid so my ph is now 7. If your worried what fish you can get for hard water I wouldnt worry too much as most tank bred species are happy with a stable ph! Its more important its stable than trying to chase a perfect number. Your ph is a good value
 
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