Re: [APD] Re: H3PO4 and Green spot algae

["Liz Wilhite" <liz_wilhite at hotmail_com>]

> Just a point in passing. Doesn't H3PO4 throw off the
> CO2/KH/pH table? By depressing pH, it should make the table
> show more CO2 than you really haveSomething to keep in mind
> if you're putting acids in the tank other than the carbonic
> you get from CO2.

No.  Those tables are based on the Henderson-Hasselbach equation dealing 
with the dissociation of weak acids.  If enough phosphoric acid is added to 
impact the carbonate buffer -- and I doubt the amount we are talking about 
does -- then not only will the pH shift but the KH will also shift.  So, if 
you add enough phosphoric acid to cause a measurable change in the pH then 
you should measure KH.  The equation is still valid.

This is why various people try to remind everyone that you should 
occasionally check KH and GH even though they appear stable.

The effect is probably not going to be all that much different than adding a 
substantial amount of KH2PO4 or K2HPO4 to a tank.

Liz


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