# DIY 4DKH Solution



## Solcielo lawrencia (Dec 30, 2013)

Do you have a gram scale? If not, your solution won't be accurate.

This is Wet's calculator. You input the desired CO2 ppm and how much distilled water you'll be adding baking soda to and it will tell you the mg necessary to reach that ppm.
http://dropcheck.petalphile.com/


----------



## jfynyson (Apr 15, 2013)

0.12 grams bicarb to 999.88 grams water to yield 1L 4 dKH solution. Then you'll need about a 0.1% bromothymol blue in ethanol indicator solution. Keep in mind this will not tell you exactly how much CO2 you have...it'll be rough ballpark.


----------



## DarkCobra (Jun 22, 2004)

jfynyson said:


> Then you'll need about a 0.1% bromothymol blue in ethanol indicator solution.


LOL, that's extreme DIY. Just use drops from a pH test kit.

You should also test your finished 4dKH solution, just to be sure. If you have a KH test kit, and the test vial contains 5mL (for example), try using 20mL of your DIY 4dKH (in a bigger container of course). Then proceed with the test as normal. Divide the number of drops by 4 to get the dKH. This trick increases the test accuracy from 1° to nearly 0.25°, but it's still ballpark.

I made my first DIY 4dKH this way. Later decided it was easier to just buy it premade. Compared the two out of curiosity and it was fairly close.


----------



## Solcielo lawrencia (Dec 30, 2013)

DarkCobra said:


> LOL, that's extreme DIY. Just use drops from a pH test kit.


The pH solution _is_ bromothymol blue.


----------



## 32Bit_Fish (Jul 8, 2012)

I have a digital scale that weighs letter. Would that work?

Why 4dkh? Why not 3dkh or 5dkh? People add 3 drops PH tester solution and green means enough CO2 and yellow means not enough CO2. The end result seems very vague.


----------



## Solcielo lawrencia (Dec 30, 2013)

No. Those scales are not accurate enough. You need one that is accurate to the hundredth of a gram, e.g. 0.12 grams. In actuality, to be perfectly precise, you should be adding 119.4 mg of baking soda to 1L of distilled water.


----------



## creekbottom (Apr 5, 2012)

Here is what I did, because my water here is OVER 4. Added distilled water and kept testing with my kH kit till I got 4.


----------



## Solcielo lawrencia (Dec 30, 2013)

creekbottom said:


> Here is what I did, because my water here is OVER 4. Added distilled water and kept testing with my kH kit till I got 4.


This is not really a good idea because other cations in the tap water, such as Ca2+ and Mg2+, can buffer the solution as well, not just CO3. So while CO3 may be 4dKH, the actual pH of the solution can be much higher than the indicated 4dK.


----------



## Hoppy (Dec 24, 2005)

http://www.plantedtank.net/forums/showpost.php?p=801218&postcount=14 is a good way to make 4dKH water. It doesn't have to be very accurate - a 10% error in KH only makes a 10% error in ppm of CO2, but the drop checker isn't anywhere near 10% accuracy even with perfect solutions.


----------



## DarkCobra (Jun 22, 2004)

Solcielo lawrencia said:


> The pH solution _is_ bromothymol blue.


I know, that was my point. Extreme to make what you can buy inexpensively at any fish store.



32Bit_Fish said:


> Why 4dkh? Why not 3dkh or 5dkh? People add 3 drops PH tester solution and green means enough CO2 and yellow means not enough CO2. The end result seems very vague.


4dKH calibrates it for green at 30ppm.
3dKH calibrates it for green at (30/4)*3=22.5ppm.
5dKH calibrates it for green at (30/4)*5=37.5ppm.

And so on. As 30ppm is kind of a standard, so is 4dKH. But you can calibrate it for anything you wish.

Also, yellow means you have _more_ CO2 than what you've calibrated it for - rather than "not enough" as you said.


----------



## Jonnywhoop (May 30, 2012)

this isnt Breaking Bad guys :icon_cool


just buy the little bottle for 2 bucks!!! :icon_roll


----------



## Darkblade48 (Jan 4, 2008)

I must admit, I make my own bromothymol blue solution


----------



## DarkCobra (Jun 22, 2004)

Darkblade48 said:


> I must admit, I make my own bromothymol blue solution


Curiosity piqued. Why?


----------



## jfynyson (Apr 15, 2013)

DarkCobra said:


> Curiosity piqued. Why?


I make my reagents b/c I have access to analytical balances as well as the indicators, salts, etc...it's funner that way IMO if you have the means.


----------



## Darkblade48 (Jan 4, 2008)

DarkCobra said:


> Curiosity piqued. Why?





jfynyson said:


> I make my reagents b/c I have access to analytical balances as well as the indicators, salts, etc...it's funner that way IMO if you have the means.


As jfynyson mentioned, because I have access to analytical balances, the salts, everything that is needed to make the solutions.

Also, I don't have a LFS close by


----------

