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Re: Aquatic Plants Digest V2 #878

>      If my tap water has a high pH simply because of low [CO2], then I
>      could bring the pH down by injecting CO2, which I already do, in my
>      aquarium.

Yep.  Same is true for anyone else whose water utility delivers high pH
water and who can return the water to a normal pH by aerating it, or just
by letting it sit.  Many inland cities in the US seem to use this
treatment process, including Dallas and at least two utilities in the
Kansas City area.

>      This means I could use a Python to change my water directly
>      from the tap; there might be a small pH spike, but it would quickly
>      equilibrate.  If I change no more than 10-15% at a time, there
>      shouldn't be a problem with chlorine, either.

Actually, for some of us it wouldn't even be much of a pH "spike".  Based
just on simple mixing calculations, if your tank starts out with a pH of
7, you drain off 15% of that and replace it with water with a pH of 10,
then the pH of the resulting mix is 7.07 (gasp!).

Once its mixed, the buffers take over and the pH will likely shift some,
with the final number depending on the buffer capacity in the mixed water.
Your tap water pH moves down to a pretty reasonable value with time and
aeration, so your tap water must not be strongly buffered (the lime
treatment pulls that down, as well).  I doubt that you would see much of a
pH swing at all, as long as your water changes stay around 15%.

Roger Miller

From Albuquerque, where due to recent rains new beach-front property is
selling cheap.