DROP CHECKER

[CBWMN]

I was looking into buying a drop checker.
Reading about drop checkers, I realize that they are only a glass container that hangs inside the tank with PH reagent inside.
I already have a KH/GH and several PH test kits. These will tell me the same thing
as a drop checker. I already check my PH levels daily.
I really don’t want more unsightly hardware inside any of my tanks.
So, why do a lot of folks recommend a DC for indicating CO2 concentration?

Thank you
Charles
:help:

 

[KarlTh]

Because the KH/pH/CO2 table only works in if the only acid is CO2 and the only buffer is bicarbonate, which is the situation you maintain in a drop checker by using distilled water and sodium bicarb only.

 

[CBWMN]

I guess I don't understand. I know you put distilled water in the DC.
But sodium bicarb?
That is just like a color on a PH chart right?
So don't you still have to use the KH/pH/CO2 table?
I know I'm a little slow but I just don't want to waste $$ if I have everything I need already.
Charles

 

[KarlTh]

The drop checker works on the basis that in water of 4KH (reached by adding sodium bicarb (which is not a colour on a pH chart but a simple way of adding bicarbonate to the system to achieve a given KH to DISTILLED water so that there is no other buffer or acid) will have a particular pH (indicated by the colour in the drop checker which also includes an indicator dye) at the desired CO2 concentration. It essentially bypasses having to manually use the table, and elimates the inaccuracies caused by the fact that most tanks do not meet the assumptions on which the table is based.

Using the table on readings from most tanks gives inaccurate results, because any other acids or (more rarely) buffers will skew the results. For instance, my tank runs at around pH 6.0 with a KH of 3; according to the table that's a CO2 level of 87ppm; that's actually off by a factor of at least three because I peat filter the water, adding extra acids.

 

[Bajanfish]

:iagree:

Before I used 4KH solution instead of my aquarium water, my drop checker showed more c02 than I actually had, even in the yellow, I had to add two more bubbles per sec to get it to green.