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Re: CO2, pH and kH
A kH of two holding your pH when adding CO2? Don't bet on it ;D My
experiences, for what it's worth:
My experiences with a DIY yeast reactor and a kH of just two has shown me that
my pH WILL crash. It's just not enough to hold the pH. The pH was well under
5.0 (all the fish were hiding and had a panicky look to them). When I put my
hands in the tank to start changing water, it STUNG me (I have a cat..always
have teeny little nicks from playtime <G>).
Several hours later and a 75% water change all had returned to "normal", a pH
of about 6.5 (which is still about 0.5 to 0.75 lower than they are used to).
Mind you I had to dribble the replacement water in so slowly it took over an
hour to do it. Everyone survived the "rapid" pH rollercoaster of the day. The
tank's kH is now kept at approximately 5 and I haven't had a single pH
problem.
Another friend also has a kH of 2.0 and his system ultimately crashed as well
(no additional CO2 to this particular system). He wasn't as lucky as me. Lost
almost every fish in his fishroom.
Susan
Several people have written:
<<Increasing your carbonate hardness (KH) will reduce pH swings associated
with variation in the CO2 supply. If your KH is 2 or more, your probably
okay.>>
<< If the KH is anything other than _very_ low, then KH has no
effect on the size of the pH swing resulting from a given CO2 concentration
change (ratio change, not difference). Check the table and see. What
the KH _does_ change is the absolute pH for a given CO2 concentration,
and that increases by 0.3 for every doubling of KH.>>
<< As Steven says, if the KH is 2, you have no problem, and you
can probably use less. What a large KH _does_ protect against is the
effect of adding strong acids. If HNO3 is generated in your tank,
then it will use up the KH, and when it runs out......>>