Why Use 4Dkh Solution

[Spurry]

Hi can some one explains why we use 4dkh solution to find out the ph/co2 levels when my water reads 2 dkh Would this not give a incorrect reading


Thanks

 

[m_attt]

Drop Checker

 

[Spurry]

The accepted practice is to fill the drop checker with distilled /deionized/RO water that has been adjusted to a known kH value. In this way the drop checker water is isolated from the tank water and only reacts to direct contact with CO2 evaporating from the tank into the checkers air bubble and then into the water sample. It was reasoned that a distilled water sample adjusted to a carbonate hardness of 4 dkH a 30 ppm concentration results in a pH of approx 6.6 which, using the reagent of a pH test kit in the drop checker turns the water sample in the checker green. 4dkH water has now become the standard solution

Would this not only work if your tank water is 4 dkh as it says if you use 5 the colour would be slightly different, what I'm getting at is if your water is 2 dkh then adding 30ppm would not give the same colour in the drop checker as 4 dkh water would just like 5 does not


Or am I just picking at something that does not matter ? And it hey it just wants to. E lime green after dosing and darker when not dosing

Cheers

 

[DrRob]

4dkh water is used in the drop checker as it has a reliable level of buffering that happens to land the colour change of the indicator at around 30ppm of CO2. The hardness of the water in the tank doesn't matter, as it should, in theory, not come into contact with the contents of the drop checker. The CO2 from the tank does though, hence the colour change.

You can, in theory, use different strengths of liquid to move the change point of the indicator for different levels of CO2.

 

[m_attt]

you want 30ppm of co2 in your tank, In 4dkh water mixed with ph indicator solution 30ppm of co2 turns the mixture lime green. So when the water in your tank reaches 30ppm it will in turn make the solution in the drop checker turn lime green.

same as when you use a liquid test kit, it does not mater what water you use or where its from, the colours it turns to read of the chart is always the same.

 

[Spurry]

Thank you both fully understand now it you have explained it that way,

Thanks

 

[Spurry]

Sorry forgot to ask, you aim for lime green is this just
When the co2 is on and it goes back to a darker green when
The co2 is off

Thanks

 

[m_attt]

Ive only used 4dkh water with bromo blue indicator solution, You can buy it premixed at aqua essentials (easiest way to do it) It starts blue when no co2, goes green when right co2 and then yellow when too much co2.

you want it to be green when the lights come on, so start it a couple of hours before lights on, then you can turn the gas off an hour before lights off. no idea what colour it changes to over night as its dark lol, at a guess somewhere between blue and green

 

[Spurry]

Ive only used 4dkh water with bromo blue indicator solution, You can buy it premixed at aqua essentials (easiest way to do it) It starts blue when no co2, goes green when right co2 and then yellow when too much co2.

you want it to be green when the lights come on, so start it a couple of hours before lights on, then you can turn the gas off an hour before lights off. no idea what colour it changes to over night as its dark lol, at a guess somewhere between blue and green

ok thats what im after it should change over night but as long as it lime green when co2 is on and light are on then it ok..

 

[m_attt]

also worth noting it takes at least an hour to change colour to show the level in the tank, so you up your gas very very slowy over the course of the day to find the correct bpm.