What to believe

[Angry_Platy]

I have DIY CO2 going into the tank and the plants are growing well so I am assuming the CO2 is good enough. Occasionally I test the water. Today was the day.

RESULTS
KH 150ppm.....8.4deg
pH 7.2
(both measured with a test kit)

CO2, measured with a test kit = 28ppm

Based on the KH and pH and the charts out there, my CO2 should be 16ppm. I had done the KH and pH tests first so when doind the CO2 test I was watching the vial closely as it got to 16ppm....but no...it went to 28ppm.....

Which is correct? Do I believe what the tables tell me or what the actual measured CO2 is?

Water was taken from the same spot in the tank for all the tests.

 

[George Farmer]

How does the CO2 test work and what make is it? What type and make are your pH/KH kits?

 

[Angry_Platy]

CO2 test is made by Azoo....add one drop of reagent one then keep adding reagent 2 until the colour changes to pink and holds the pink colour.

pH test kit is made by wardley.....add reagent and measure against colour chart.

KH test kit is Hagen. Add one drop of reagent to turn it blue. Then add dropwise until colour changes to yellow/lime green colour.

I mean, if it was only a small discrepancy I wouldn't be concerned. But when it is like nearly half....double....its a bit confusing.

 

[George Farmer]

How accurate is your pH test i.e. what increments are they?

 

[Angry_Platy]

0.2 increments....so.....7.0, 7.2, 7.4 etc.

 

[George Farmer]

That's a tough one to decide then. As long as your fish and plants are happy then I wouldn't worry too much. Keep an eye on your pH and you'll be fine. I understand your frustration though. I couldn't understand why my KH kept creeping up for "no reason". I then discovered my fine gravel contains lime. That's one reason I perform 30% weekly water changes with RO - to keep the hardness down for my softwater fish (and plants).

 

[The Mohave Kid]

I'd go with your test kit and observations of your fish .. many tables I have seen are based on assumptions that do not apply to real tanks ... for example a concentration of acids other then carbonic will invalidate the table ... and there are many other acids in a aquarium besides Carbonic.

Good Day ... B)