Re: [APD] CO2 Measurement Method

[Vaughn Hopkins <hoppycalif at yahoo_com>]

I also have a couple of small "driftwood" pieces, which I boiled 
thoroughly before using.  I got lots of brown water during several 
cycles of boiling.  It is possible that tannins are being leached out 
there too.  Do any of our chemists have an opinion?  Will tannins give 
us a low PH reading and make it look like we have more CO2 than we 
really have?

When my KH/PH readings said I had 70 ppm CO2 I still had some BBA, so I 
jacked up the CO2 even more - still no fish distress.  Now I have no 
visible BBA - just some diatoms and a bit of hair algae, which I keep 
removing.  My kingdom for a simple, foolproof CO2 meter!!

Vaughn H.
On Tuesday, January 31, 2006, at 12:09 PM, Rory O'brien wrote:

> I'm suffering similar confusion Vaughn; the other night my KH measured 
> 6.5
> and my (electronically tested) pH was 6.4, suggesting a CO2 level of
> around 77ppm. Live and apparently happy fish would suggest otherwise 
> but
> there's no other buffering going on (that I'm aware of). I have 
> dialled it
> back some anyway.
>
> Quoting Vaughn Hopkins <hoppycalif at yahoo_com>:
>
>> I have a cork wall in my 29 gallon tank.  I also have been measuring
>> 150 - 250 ppm CO2 using PH/KH table.  Being somewhat dim witted it has
>> taken far too long for me to connect those two facts.  Apparently cork
>> leaches tannins into the water which drops the PH a bit, making the
>> PH/KH/CO2 table inaccurate.  Today I checked a water sample taken from
>> the tank last night and allowed to sit over night vs. one taken this
>> morning.  Last nights sample had KH of 9 degrees, PH of 7.0 - 27 ppm
>> CO2.  Todays fresh sample had KH of 9 degrees and PH of 6.2 - 170 ppm
>> CO2.    I think this strongly indicates that the cork is fouling up
>> the
>> CO2 measurement.   But, the .8 drop in PH should mean my actual CO2 is
>> about 25 - 30 ppm, which the fish and plant reactions say it should
>> be.
>>   Any comments?
>>
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>
>
>
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