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

[Clint Brearley <clint_brearley at telstra_com>]

Thanks Ann and Scott. I'm pretty sure my CO2 levels are okay - high enough, but not too high, but I'm just curious as to the actual concentration. I think the main problem is just my ability to read the pH test results. I already do the double volume KH thingy - always comes up b/w 4.5 and 5 (tap water is only 11ppm so I have to add NaHCO3).

I think I'll hold off on the CO2 test kit. Based on the low stability of the reagents, I don't think I could ever really trust the results anyway.

I'll try purging the water sample of CO2 as you suggested, Scott, and see the effect on pH (btw - I have another non-CO2 tank with similar water parameters and the pH always reads 7.2-7.4, so I think the kit is okay).

Also, I have access to a good quality pH probe at work, so I thought I might bring in a sample in a tightly sealed container filled to the brim and test that. CO2 loss from the sample should be insignificant if it's well sealed don't you think? I'll also test the purged sample. If the readings disagree with my test kit then I think I'll look into getting a better quality pH kit.

Thanks again

Clint Brearley
Melbourne, Australia

> From: "Ann Viverette" <annv777 at houston_rr.com>
> I have an Iron and CO2 test kit from Red Sea that is about 12 
> months old and
> no longer works. At least the CO2 part no longer works, it did in the
> beginning, for I checked it against the charts and they agreed. I 
> don'trecall when I used it last, it may have been not reactive for 
> many months
> now.

> From: "S. Hieber" <shieber at yahoo_com>
> 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.


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