CO2, no need to measure KH ??

On Thu, 12 Jan 2006 15:36:11 +0000, Nikki Casali wrote:

wrote:

[20 quoted lines suppressed]

I only use a pH meter to determine the levels of CO2 in my aquariums at
any given moment. The KH is usually a constant, so you only need to ever
measure that once, unless you are producing your own KH level from a
reverse osmosis filter or rain water. Actually, it is sometimes possible
for KH to vary from your tap, especially if you live in a hot and dry
region. The water authorities will sometime switch water sources, one
with more rain water etc, thus changing the KH.

CO2 content is not the only substance that can reduce or affect your pH.
Phosphate is known for altering the pH. Acids leeching from decomposing
dead matter or even drift wood can affect it. So you may need to take
these issues into account.

Nikki

Yes, good points Nikki, thank you.

This all began with a post in another forum from a member who had a GH test
kit but no KH.
We were asked how to convert GH into KH for CO2 measurements !

While the discussion progressed I was looking at the KH-pH-CO2 chart and
was intrigued by the constancy of the pH drop for a given CO2 mg regardless
of the actual KH. iyswim.

Not having seen mention of this in my various internettings I thought I'd
ask for thoughts here
As you say, once a person is familiar with their KH changes (or lack of)
with time then both systems of targeting CO2 level would be good.

Since then a member has come up with the maths behind the constancy of the
pH drop for a given CO2 level across all KH values, so I am now happy that
I am not either mad or doing something wrong !

Regards.