# Drop checker color = what concentration of [email protected]



## cbwmn (Dec 18, 2007)

This is probably a dumb question.
I bought two drop checkers on ebay and 
some 4dKH solution to put in them.
There are three colors on the color chart. 
Blue then green and then yellow at the top.
How do you determine the CO2 concentration 
using only three measurements?

I assume blue is no CO2, green is supposedly the right concentration 
and yellow is too high.

I’ve done a search and cannot seem to find what the colors indicate.

Charles


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## hooha (Apr 21, 2005)

with a 4dKH solution, the 'green' is supposed to be 30ppm. The blue means less than that, the yellow means more than that


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## cbwmn (Dec 18, 2007)

Before I bought the DC's, I tested KH and PH and calculated the CO2
saturation. 
IMO, that was way more accurate than blue=0ppm, green=20-30 ppm
and yellow is something beyond that.
Prior to buying them, I started a thread asking why a person needs them:
http://www.aquaticplantcentral.com/...um-plants-discussions/59518-drop-checker.html

Recently on my 46G BF, the solution is staying in the green even though I stop
injecting DIY CO2 at night. It's the same color in the morning as it was the previous night. I stopped the CO2 at night because the DC color went yellow.

I'm not sure that the DC is the way to truly check CO2 concentration.

Charles


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## hooha (Apr 21, 2005)

the theory behind the drop checker is this - with a 4dKH solution, you have a an indication of your target range, when it's too low, and when it's too high. The other values are not necessary to know them absolutely. 

There are shades of colors with the indicator solution as well.

dark blue = something's wrong with the CO2 injection, check it out
blue-green = CO2 levels are on the low side, increase bubble rate a little bit and recheck in a few hours
green = CO2 levels are adequate
yellow-green = CO2 levels are adequate, monitor to make sure it doesn't go much higher
light yellow = CO2 levels are too high - check your bubble rate and cut back

You can assign actual numerical values to it, but the usefulness doesn't get any better with the numbers.

Also, the accuracy of KH reagents often comes into question.


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## Crispino Ramos (Mar 21, 2008)

hooha said:


> the theory behind the drop checker is this - with a 4dKH solution, you have a an indication of your target range, when it's too low, and when it's too high. The other values are not necessary to know them absolutely.
> 
> There are shades of colors with the indicator solution as well.
> 
> ...


thanks for the useful info


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## cbwmn (Dec 18, 2007)

I'm beginning to wonder about my 4dKH solution.
Charles


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## hooha (Apr 21, 2005)

you can always try testing it


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## cbwmn (Dec 18, 2007)

hooha said:


> you can always try testing it


hooha
I checked it using a 6 mnth old (from Petsmart)API GH&Kh test kit.

It took 7 drops to turn the solution to yellow.
7 drops = 7dKH
It took 5 drops of the indicator to turn it too blue.
I think I'll try making my own solution.
Thank you
Charles


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## hooha (Apr 21, 2005)

are you sure that's correct? I thought 1 drop = 0.5 KH, but then again I haven't used that brand in a long time.


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## cbwmn (Dec 18, 2007)

hooha said:


> are you sure that's correct? I thought 1 drop = 0.5 KH, but then again I haven't used that brand in a long time.


Yes, the KH&GH conversion chart show #of drops = degrees KH
It's 2:20 AM, I'll test again tomorrow.

The reason I'm skeptical is the DC went into yellow last week. 
I stopped the DIY CO2 and the DC stayed yellow for a long time. 
When it came green, it stayed green and never went back to blue.

I once OD'd my angels (yes, I've read thats impossible w/DIY, but it does happen).
Woke up one morning, they were laying on their sides and gasping. Did an 80% WC,
threw in airstone and they all recovered.
I use an XP2 on my 46 g BF, and I have the spraybar way down close to the bottom,
so there is very little surface movement. 
I inject the CO2 into the intake tube. Lighting is 2 WPG (96 w A&H retrofit)
I used to use 3 cups of sugar to 1/2 gallon of water. 
I'm now only using 2 cups to cut down on the intensity.

Thank you for your input.
Charles


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