# made 4dkh in small quantities



## neilshieh (Jun 24, 2010)

well i got a whole bunch of test kits at petmountain.com with free shipping as an early christmas present and decided to make the 4dkh solution. well anyways i tested our tap and it was 7dkh and my drinking water 2dkh 
and then i just mixed them in amounts using a cc syringe. 
and i was able to make 4dkh in small quantities 
here was my results 
1/2 oz + 25cc of 2dkh drinking water 
1/2 oz + 5cc of 7 dkh tap water 

and yes i'm aware that i can simply the amounts but i made a mistake when i was adding the water so that's why that extra 5 cc is there 

so now i have 4dkh... do i just add ph tester until its blue and then i'm done?
this was easy for me because i didn't want to go through the baking soda stuff and distilled water.
did i do something wrong? feel free to burst my bubble


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## Left C (Jun 14, 2005)

neilshieh said:


> well i got a whole bunch of test kits at petmountain.com with free shipping as an early christmas present and decided to make the 4dkh solution. well anyways i tested our tap and it was 7dkh and my drinking water 2dkh
> and then i just mixed them in amounts using a cc syringe.
> and i was able to make 4dkh in small quantities
> here was my results
> ...


:laser:









The pH/KH/CO2 relationship is valid if there are only carbonate based buffers in distilled water. This is why we use baking soda and distilled water. It isn't valid with any other components that I know of.

Still, even using the correct components, we only have an approximation of the CO2 levels in our aquariums. Using the wrong components throws it off even farther.

You can test your tap water. It most likely has a moderate level of phosphates. This is one of the reasons why your KH is 7. Phosphates are much stronger buffers than carbonates. Your results will skew your approximation of your CO2 level to the high side. In other words, your "falsely" tested CO2 level may indicate that you have 60 to 160 ppm of CO2. How much would this faulty information help you?

You can't cheat mother nature. Chemistry and physics in this case. 

The drop checkers only work fairly well. They are slow to indicate and a "green" color may indicate a 15 to 45 ppm level. Give them the best chance that you can by making as accurate a buffer solution as you can.

A better test kit to use is Lamotte's Alkalinity test kit (MODEL WAT-DR • CODE 4491-DR). The color changes are rather abrupt. The test solution can be three different colors: green, purple and red. Green is before the titration is finished. Purple is the endpoint and red indicates that you went past the endpoint. It is a very good test kit and it isn't very expensive.
http://lamotte.com/images/pdfs/instructions/4491-dr.pdf
http://www.marinedepot.com/LaMotte_...water_Aquariums-LaMotte-LM1111-FITKAL-vi.html


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## neilshieh (Jun 24, 2010)

>.> well ill try it out anyways...


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## Seattle_Aquarist (Mar 7, 2008)

Hi Neilshieh,

+1 for Left C's comments. The solution may (and probably will) change color; but still be inaccurate. We don't use tap water for the same reason we don't use aquarium water in our drop checkers. $` for a gallon of distilled water is cheap.

Inaccurate drop checkers can cause overdosing of CO2 with the result being loss of fish and inverts. Not a chance I am willing to take.....


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## Left C (Jun 14, 2005)

neilshieh said:


> >.> well ill try it out anyways...


This picture reminds me of your comment.


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## darkoon (Jun 7, 2010)

i too made 4dKH solution out of tap water, had no idea about validity of pH/KH/CO2 relationship. Thanks Left C for pointing it out. Just remade it with purified water, eager to see how the color change tomorrow.


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## Left C (Jun 14, 2005)

Chuck's CO2 calculator/chart went into detail about the pH/KH/CO2 relationship. It is too bad that it is gone. Here is part of it:

"*The pH-KH-CO2 Relationship*
_pH, KH, and CO2 have a fixed relationship as long as carbonate is the only buffer present_ (no phosphate buffers like pH-UP and- DOWN, Discus Buffer, etc). There are some parts of the country that have high levels of phosphates in their water supply. For those cases, determining CO2 levels will be difficult, as the phosphate will throw off the pH-KH-CO2 relationship, which means the CO2 charts and calculator below won't work. Note that the commercially available CO2 test kits will also be invalidated by the phosphates.

NOTE: This calculator (and the chart based on this formula) will only work if your water is carbonate buffered. If your water contains high levels of phosphates, it will alter your water properties, and invalidate these CO2 calculations."
From: http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

I'm sure that you've read about people having very high amounts of CO2 in the water, like 70 to 100+ ppm or so, and the fish were fine. This was caused by the phosphates and other acids and bases in the aquarium invalidating the pH/KH/CO2 relationship.

Hoppy wrote a good deal about it when he was working with drop checker solutions. Good reads!


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## neilshieh (Jun 24, 2010)

thanks or the advice! with distilled water its even easier! i made a small bowl in 5 minutes. i got a small bowl, poured in distilled water and tested it. it was 0dkh, then i got a disposable fork and scooped a minute amount on one of the teeth's very edge. after 4 little scoops i tested and got 4dkh.


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## Left C (Jun 14, 2005)

Left C said:


> Chuck's CO2 calculator/chart went into detail about the pH/KH/CO2 relationship. It is too bad that it is gone. ....


I found Chuck's pH/KH/CO2 relationship article called "Measuring CO2 levels in a Planted Tank." It is a good read! Notice that he mentions that this relationship is only valid if the only buffers present are carbonate based several times. I got this from coach_z @ aquariacentral.com .

http://web.archive.org/web/20080610123231/www.csd.net/~cgadd/aqua/art_plant_co2chart.htm


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