Re: [APD] Nitrite toxicity and GH

["Robert T. Ricketts" <rtricketts at verizon_net>]

Stuart Halliday wrote:
> Hi,
> I was wondering if anyone can help me.
>
> I'm trying to understand the relationship of Chloride to GH in a 
> freshwater tank with regards to nitrite toxicity.
>
> I understand that from a level of GH you can work out how much 
> Chloride is in a tank and therefore if it is enough to suppress a 
> certain level of nitrite toxicity?
>
> Is this right?

In a word, no.  Nitrate or nitrite play no role in General Hardness, and are
undetected by that test.  Unfortunately there is no available test kit for
us to detect chloride ion in freshwater.

But yes, chloride ion does block nitrite toxicity in freshwater fish, by
competitive inhibition - competition for the binding site on the hemoglobin
molecule.    I have seen recommendations as low as one-tenth teaspoon per US
gallon (from the Skeptical Aquarist), but I have used significantly more -
but still quite low dosage - at one quarter to one-half teaspoon per US
gallon without problems.  

If you are concerned with the sodium ion, potassium chloride will have the
same effect as would ordinary salt (sodium chloride).  Potassium chloride is
the material in many slat substitutes available from the grocery stores.

RTR
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