# How to make 4dKH?



## NeocaridinaCollector (Mar 12, 2011)

Hi guys,
So I bought 2l of distilled water and some bicarbonate of soda. I want to make some 4dKH solution for my DIY drop checker but I lost the measurements to make it.
How much bicarbonate should I add to make 2 litres of 4dKH? And what is the exact process?
Cheers,
JK


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## fresh.salty (Jul 2, 2010)

I just added a little to some water and tested. My goal was to make 16 dKH and then dilute it. I think that made it easier to test with less margin for error with my test kit which is one drop equals 1 dKH.


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## Darkblade48 (Jan 4, 2008)

Here you go:

http://www.plantedtank.net/forums/planted-tank-faq/42429-kh-standard-how.html

Found using search in < 1 minute.


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## NeocaridinaCollector (Mar 12, 2011)

Thanks guys.
Darkblade that is the thread I read, but I just couldn't find it when I searched.
Cheers


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## Hoppy (Dec 24, 2005)

If you rely on your KH test kit, be sure to get an up to date one, not one with lots of shelf time on it. I like the idea of making much higher KH water first, then diluting it later to get to 4 dKH. When only 4 drops indicates 4 dKH, the error, even with a perfect test kit, is +/- .5 dkH, or about +/-12%. But if you make 16 dKH water, the error is down to +/- 3%. And, by testing a double size sample of water, you can reduce that down to less than +/-2%. But, you have to start with a KH test kit you can reasonably expect to be accurate. (I really doubt that any hobbyist test kit is accurate to better than +/- 10-20%, but calibrating a KH kit is very difficult.)


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## NeocaridinaCollector (Mar 12, 2011)

So say instead of testing 5ml I test 20, that should give me a more accurate reading right?
Also how much of the 4dKH should I use in my drop checker? Does the amount matter?


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## Disco Dan (Mar 17, 2011)

They way I did it was to empty the tank out of my dehumidifier (free distilled water!) into a glass jar (about a liter) then I added a tiny pinch of baking soda and tested the water. Then I used a large syringe to add/subtract water until the test kit gave the correct reading. 

Not the most accurate from what you will find on other threads but took about 30 minutes to do. 1 liter will last you a long time - my drop checker uses only 1ml of water and they last several weeks so you wont need much. 

I also test the water prior to using it in the drop checker - I have found it had changed slightly (which could be down to the accuracy of my aging test kit).


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## Cwy0608 (Aug 27, 2013)

i happen to have 4kdh standard solution I can use that? How do I use it in my drop checker? According to my Chinese drop checker instructions I use 5ml Solution (in my case 4kdh) and 15 ml of tank water. 

Am I correct?


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## Darkblade48 (Jan 4, 2008)

Cwy0608 said:


> i happen to have 4kdh standard solution I can use that? How do I use it in my drop checker? According to my Chinese drop checker instructions I use 5ml Solution (in my case 4kdh) and 15 ml of tank water.
> 
> Am I correct?


If you have 4 dkH reference solution, just use that directly. You do not need want to mix it with aquarium water.

Fill your drop checker about half full with 4 dkH reference solution, and then add a few drops of bromothymol blue so that the colour is easy to see, but not completely opaque.

Upon addition of bromothymol blue to your 4 dkH reference solution, it should turn blue. If it does not, then your 4 dkH reference solution is likely bad/improperly made, and you should make/purchase some new solution.


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