Re: Aquatic Plants Digest V2 #85

> Help. Where does ammonium come from? I thought ammonia was what the fish
> secrete. If so, something must first turn ammonia into ammonium ... Where
> does that something come from? TIA.

	Ammonia is what the fish excrete, you're right. Ammonium is just 
the form of ammonia that exists in environments that are acidic. The 
ammonium is just the protonated form of ammonia -- ammonia=NH3, 
ammonium=NH4+. Nothing "converts" ammonia to ammonium. It is just a 
physical phenomenon related to the concentration of NH3 and the relative 
availability of H+.

> A related question: when one has a biofilter in a heavily planted tank,
> would the bacteria and the plants be in competition?

	Yes, that's right.

> If so, who gets what first?

	The both get some. But, the total amount available to the plants 
is reduced because of the competition with the bacteria in the filter.

> the water through while the plants stand around waiting. Thus, the plants
> are more likely to get only nitrates--which we now know they have a harder
> time making use of.

	Your picture of what is going on is a little off. Think of it like
this - You are in a closed room with a burning candle. The candle is also
using up O2 and therefore you are competing with the candle for oxygen.
Because of the candle, at any point in time, the amount of oxygen that you
had available to you was less that there would have been if the candle had
not been there, right? 
	Also, the concentration of NH3 or NH4 in your tank is
theoretically _never_ zero. When we say that the test kit reads 'zero', we
really mean that the concentration is *undetectable*.