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Re: [APD] So what are my CO2 levels really?

You have a pretty wide margin of error there. Towards the
lower end, you're not liekly to see any problems indicated
by fish behavior. Towards the upper end; that would be way
too high.

If the fish show no signs of stress, I would assume that
the CO2 level is down below about 40 ppm and maybe no
higher than about 30.

You shouldn't have to get a pH monitor to get a useful pH
measurement, although they certainly make accurate readings
easier. With a different brand of test kit, you might read
the pH at a diff level than the kit you are using.

For the KH, if you're measuring one degree per drop of
titration fluid, then try doubling the size of the sample
water and count each drop as 1/2 degree. This will get you
a slightly more accurate reading for the KH.

Of course it's possible that some organics or other source
of acidity is throwing things off.  To see the effet of hte
CO2 on you water. take a sample, shake vigorously and then
let stand overnight. Virtually all the "added" CO2 should
be gone by then. Measure the pH and see were it's at. The
diff between that and your prior pH measurements are the
result of the added CO2.

Hope that helps.
--- Clint Brearley <clint_brearley at telstra_com> wrote:
> I tested my pH last night and this morning and it is
> around 6.2-6.6 (I think?), KH 4.5-5, so CO2 is around
> 35-90ppm. This just can't be right, can it? If levels
> were that high then I would expect to see the fish
> stuggling to breathe, but they all look just fine. Plants
> are always pearling, so oxygen levels are high.
> Tank is 48x14x18" 50gal, 42gal (160L) water column,
> 2.4wpg T8 FL, nitrate 5-10ppm, phosphate 0.5-1ppm, KH 5,
> GH 8, CO2 1 bubble/second 24/7, DIY external reactor
> powered by 375 LPH powerhead, filtration fluval 204, CO2
> and filter outlets below water level, moderate fish load,
> 50% weekly water changes.
> The kit is an old AP kit (bromothymol blue indicator), I
> think it still should be okay. Am I just reading it
> incorrectly as the colours aren't very distinguishable
> IMO. It looks a yellowy-green colour to me.
> Is the pH correct, but some other acid is throwing off
> the CO2 charts? Could PVC cement be leaching from the
> reactor and lowering pH?
> I thought maybe I might just get a proper CO2 test kit.
> Do these work okay? Or am I better off with a more
> accurate pH kit or pH probe (probably don't want to spend
> that much though).
> Anyway, the plants are happy, the fish are happy, it's
> just me who is stressed ;-). I'd really like to know what
> my CO2 levels ACTUALLY are!

S. Hieber

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