# Help with measuring KH using API test kit.



## Zak Rafik (9 Sep 2014)

Hi everyone
I want to test my KH for my tank but I'm kind of not sure on one issue. 

The test kit says to add the solution until it changes to yellow color. At the same time it says "bright yellow". 

I know the solution is blue but my sample changes to a somewhat dull or dirty yellow after just 3 or 4 drops. 

If I want a deep yellow, I have to add 5 or 6 drops. 

So where do I stop? Is it once I see any trace of a yellow tint colour  or a deep yellow. ?

Thank you. 
Raffik


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## Julian (9 Sep 2014)

If you're trying figure it out so you can find out what your pH needs to be, you're wasting your time. Just up your CO2 SLOWLY until your fish start to look distressed.


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## Zak Rafik (9 Sep 2014)

Hi
Yes I have have been given this advice several times. 
But even if the test is not so accurate I'm interested to know at what stage should I stop? The moment there is a yellow tint or a deep yellow.?

Cheers
Raffik


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## ceg4048 (9 Sep 2014)

Assume 5 drops Raffik and just carry on. Do not lose sleep over this. Trying to outsmart your test kits is simply not worth the energy.

Cheers,


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## ltsai (9 Sep 2014)

Why are you testing KH? To see whether you should get the appropriate PH drop for C02 after lights on?


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## dw1305 (9 Sep 2014)

Hi all, 
Clive is right, "5 drops", but it really doesn't make any difference. 

Technically because this is a (weak acid/weak base) titration, you should go to the "end point", that is when you reach a colour where another drop of reagent doesn't change the colour. 

If the colour is the same at 6 drops ("deep yellow") as it was at 5 drops ("deep yellow"), 5 drops is the "end point".

cheers Darrel


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