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Another DIY 4*dkh Solution

11135 Views 31 Replies 17 Participants Last post by  Aquaticz
Ok, so I decided to see if I could come up with another simple and somewhat accurate method to make 4* dkh for my co2 drop checker. This is what I came up with, I verified my results by duplicating the test 3 times and ending up at the same result each time.

Couple primers to start:
- I use my own RO/DI 0 tds water for the solution
- I use a calibrated HM Digital TDS meter
- I use API's Kh test kit
- I have used both Seachems Alkaline Buffer and Baking Soda and both test out the same
- I used everyday CLEAN containers and measuring cups/spoons that are used only for my tanks use and cleaned/rinsed with RO/DI water
- I do have lab testing background and have made very accurate 4* solutions but wanted to come up with another A.S. version for the casual hobbyist.
- No it will not be "laboratory" grade/accuracy but in my experience it is close enough for the casual hobbyist.
- I have been in the hobby for over 20 years but new to the forum

1. Start with 6 cups of 0 TDS water in a clean measuring container
2. Add 1/8 tspn Sodium Bicarbonate to the 6 cups of water and mix
3. Pour out 3 cups of this mix and discard
4. Add back 3 cups of 0 TDS water and mix
5. Pour out 3 cups of this mix and discard
6. Add back 3 cups of 0 TDS water and mix
7. Pour out 1 cup of this mix and discard
8. Add back 1 cup of 0 TDS water and mix
7. Water comes out to +/- 70 ppm TDS and will test @ 4* DKh solution

Any questions or comments welcomed. And if someone has the same basic matierals, I would like to hear if you were able to duplicate my results :)


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Hi, thanks for the great article...
I have a doubt here.. I have Co2 drop checker bulb, i can prepare 4dhk solution using the above mentioned method, now what about the PH indicator solution that turns the liquid color to blue. How to prepare that solution or is there any way to test co2 level only using this 4dhk solution?? ..
The indicator solution is called bromothymol blue. Its what comes in an API pH test kit. Just add a few drops of that to your 4dkh solution in a drop checker, and you're good to go
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