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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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Hoppy wrote this- I saved it - here it is again
Hoppy wrote

It looks like any of the drop checker varieties will work as well as any other. The most effect the differences would have is in the response time, and that seemed, in my testing, to be about 2 hours no matter what the differences in design were.

The solution to use in the drop checker is water having nothing in it that affects either the pH or the KH other than carbonates/bicarbonates. The easiest way to do that is to use distilled or DI water and add sodium bicarbonate (baking soda) to get the KH you want, which is 4.0 if you want the solution to be green at 30 ppm of CO2 or 5 if you want it to be green at about 40 ppm, which is almost too high, in my opinion. The accurate way to get a known KH is to weigh dried bicarbonate of soda and add an accurately weighed amount to an accurately measured volume of distilled water to give ten times the KH you want, then mix an accurate amount of that water with 9X as much of distilled water, which will give the desired KH. For the amount of dried sodium bicarbonate to use, add 4.99 grams to 5 liters of distilled or DI water. This makes 40KH. Add 10mls of this to 90 mls of distilled or DI water to make a 4KH solution. Then add enough drops of pH reagent to get a strong blue color, but still transparent. It is best to do this only to very small quantities of the 4dKH water, not a big bottle of it.
Hoppy 2

This is a setup of two bodies of water with a air passage connecting them. CO2 goes into solution and out of solution very easily, so there is a constant flow of CO2 from any body of water and the air in contact with it, going both ways. This means an equillibrium must be reached, where as many CO2 molecules enter the air (or water) as leave it. So, two such bodies of water will both reach equillibrium with the air passage connecting them and both must have the same ppm of CO2 for that to be so. If one body of water changes in CO2 concentration, that changes the amount of CO2 in the air passage contacting that water, and that change then changes the CO2 concentration in the other body of water until it is equal to the first one. All of this takes place pretty slowly, like over an hour for equillibrium to be reached.

Wet wrote this ....

From wet's site

Reference KH for target CO2 calculator
1) Add 451.9 mg of baking soda to 1 Gallon of DI water for 4.0 dKH. Fully dilute.
2) Add the contents of this mixture to the drop checker, then add a couple drops of Bromothymol blue to the drop checker.
The range for "green" in this drop checker is 18.9 - 47.5 ppm CO2. The perfect green (shade, reaction between Br. Blue and CO3) is 30.0 ppm CO2.
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My target CO2 is [Control]ppm
I have a [Control][Control]Liter [Control]Gallon container to mix with (recommend at least 2L)
I have [Control]one [Control]two drop checkers.
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