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Re: NH4NO3

	Don't add more than a tiny amount.  The NH4+ ion is in a _very_
fast equilibrium with NH3.  The concentrations of the two are equal at a 
pH of about 9.25.  At pH 8.25 the NH3 concentration is 1/10 of the
NH4+ concentration, at pH 7.25, 1/100 of it, and so on.

	If you add just a small amount of an ammonium salt, it's the same
as adding ammonia - the pH of the solution will be decided by the main
buffer system there (HCO3-/CO2, usually), and the proportions of NH3
and NH4+ in the solution will be as above.  Ammonia toxicity to fish is
well known, so be careful with it.

	If you were to add lots, the NH4+/NH3 system could _become_ the
main buffering system.  I don't think you want to go there.

Paul Sears        Ottawa, Canada