# Where can I buy a PH drop checker?



## Patrice (Mar 8, 2006)

Hi, I am looking for somewhere on the internet where I can buy a ph drop checker. 
does someone can help me?

thx


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## hoppycalif (Apr 7, 2005)

Patrice said:


> Hi, I am looking for somewhere on the internet where I can buy a ph drop checker.
> does someone can help me?
> 
> thx


Here is the Red Sea unit from Big Al's Red Sea CO2 Indicator at Big Al's Online
Here is an ebay store selling glass drop checkers eBay Store - T 1Brian-Aquarium Plants Supplies: CO2 Diffuser, Miscellaneous, Fertilizer


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## Patrice (Mar 8, 2006)

Great! thank you! that's exactly what I was looking for

Do you know if one is bether than an other:
eBay: NEW!! Co2 Drop Checker-Highest quality handmade glass (item 250068719948 end time Jan-07-07 09:50:59 PST)

eBay: Co2 Drop Checker-monitoring proper dosage of CO2 (item 250069035332 end time Jan-31-07 16:21:09 PST)

also, what solution do you use in this? a kh ref solution?

Thanks


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## hoppycalif (Apr 7, 2005)

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.


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## Patrice (Mar 8, 2006)

thank you for the advise. 
That I understain, the reason why this work, it's beacause the CO2 in the water get into the checker and then make the solution turn to green. That's fine but after a while, will CO2 not accumulate in the checker to reach a CO2 level higher than it is in the tank?


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## hoppycalif (Apr 7, 2005)

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.


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## Patrice (Mar 8, 2006)

thank you!


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