Re: [APD] CO2 Measurement Method

["Rory O'brien" <rory_obrien at stonebow.otago.ac.nz>]

I too have several largish pieces of bogwood in there which initially
leached some degree of tannins (as evidenced by a yellowish tinge to the
water, removed with carbon). They've been in there for quite a while now
and the water remains clear.

Fish may still be the best CO2 measurement devices but I can't find
digital ones...

- R.

> 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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