Re: Re: ph Control

[cfonda@sentientconsult.com]

Peter wrote:

>The charts express CO2 concentration (in mg/l or ppm) as a function of pH
>and KH...  Does this mean that pH and KH regulate maximum dissolved CO2 ?
Somewhat... how much carbonate, CO3 (2-), will dissolve in the water is a
complex function of pH and temperature.  The variation you will see from
temperature in the range most of us keep our fish tanks (68-86F,20-30C) is
minimal.  KH comes into play as an indirect measure of how much CO3 is
already disolved in the water.  There are, however, other factors
regulating pH -- eg. the amount of tannic acid in the water from peat,
logs, etc.

>I am running in a new 55 gl. tank using peat as part of the substrate,
>rather than using it as a filter media.  Plant growth rates (in
combination
>with clay, pumice - to prevent caking -, and gravel) are absolutely
awesome
>in this substrate.

Ain't peat great.

>I had to disconnect my yeast-CO2 supply, since pH was
>reaching 6 and my KH=5 indicated - according to the pH/KH/CO2 table - that
>CO2 levels should have killed everything in the tank.  However, my school
>of Corydoras melanistus are doing perfectly.  I am now at pH=6.5 and KH=5
>which, again, according to the table, should mean CO2 levels way above the
>suggested maximum of 25 mg/l.  But the fish don`t show signs of distress.
>Can I have lower dissolved CO2 levels than the table suggests for the
pH/KH
>values mentioned previously, because of the peat in the substrate ?
Yes, you can have lower levels than the tables suggest... the tables do not
account for all possible factors and assume pure water with Ca(CO3)2 and
CO2 added only.  It would be impossible to generate tables that do account
for all possible factors.  I do not use any of the tables myself... if my
fish and plants are doing fine, I judge everything to be good.  The trick
is to observe the fishes' behavior and condition daily... if their behavior
or condition seems wrong, it is time to start wondering what might be
causing it.  I use do-it-yourself CO2 systems on some of my current tanks
(I will be investing in a digital pH regulation/CO2 system on my next tank)
and have had no problems over the past two and a half years.  In fact,
other than the occassional weak tetra which died within two days of
purchase, I have not lost a fish to a cause other than old age or murder (I
have an angel who kills any other angel we put in the tank with him) in
about 6 months.

- -- Cliff