questions on kH and PO4 dosing

[juggler]

For those dosing PO4 into your tank, does the PO4 affects the true value of kH or it doesn't matter?

Is CaCo3 in coral chips the only compound contributing to kH? Whereas only the Mg++ and Ca++ in corals contribute to GH?

[bclee]

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On 3/31/2003 11:22:36 AM

For those dosing PO4 into your tank, does the PO4 affects the true value of kH or it doesn't matter?

Is CaCo3 in coral chips the only compound contributing to kH? Whereas only the Mg++ and Ca++ in corals contribute to GH?
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True KH is strictly refering to CO3 and HCO3. Measured KH OTOH will be affected by other buffers like PO4.

At the level of dosing PO4, it will not affect the KH reading. I think it will take about 12ppm of PO4 to increase KH by 1°.

Any compound with HCO3- or CO3-- will contribute to KH... like NaHCO3, etc.

Mg++ and Ca++ are the 2 ions contributing to GH. I know the test measure bivalent cations. In the water, they are mainly the 2 ions mentioned.

[FC]

As far as I know coral chips are CaCO3. It may contain other impurities. I doubt it contribute any meaningful Mg. Can expert clarify this?