Thanks for the chemistry explanation RTB, and is what was told to me by
those I asked, though they didn't have the reason why, nor had it come to
their attention, regarding pressurized systems using up the KH faster than
open gravity fed filters.

When you mentioned higher fish loads, I went Ah Ha, but than said, "Wait."
Case in point, one of our ponders started out with pressurized, and was
about ready to take out stock in Baking Soda the way he went thru it. He
has since converted to a gravity fed filter, and says it's a rare day that
he needs BSoda... and his fish have gotten bigger in the meantime. So there
has to be something directly to do with that type of filter, not the pond,
per se, imo. ~ jan

On Tue, 17 Aug 2004 00:32:28 GMT, "RichToyBox" wrote:

The KH is consumed to an extent with all filters. The bacteria use the
carbonates to help with the digestion/conversion of ammonia to nitrite,
giving off a Hydrogen ion, and then in the conversion of nitrite to nitrate,
2 Hydrogen ions are given off. These hydrogen ions are acid and they use
the carbonates to neutralize the acid and convert the hydrogen ions with CO3
to CO2 and water. The pressurized filters, bead filters are generally
associated with heavier fish loads than the garden pond with smaller
filters, and therefore more food to be converted, more acid, more demand for
carbonates/bicarbonates to prevent a pH crash.

~Power to the Porg, Flow On!~