Ammonium and nitrifying bacteria

I wrote:

> > Your picture of what is going on is a little off. Think of it l
> > this - You are in a closed room with a burning candle. The candl
> > using up O2 and therefore you are competing with the candle for 
> > Because of the candle, at any point in time, the amount of oxyge
> > had available to you was less that there would have been if the 
> > 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 
> > really mean that the concentration is *undetectable*. 
Karen wrote:
> True, but that's not exactly the same situation as we have in an 
> aquarium.  We definitely have a finite amount of nitrogen 
> available. (in whatever form)  It is _absolutely_ possible to have 
> a situation where there is little enough nitrogen (in whatever 
> form) available that the plants are nitrogen limited.  

I write:
	In the closed room, there is also a finite amount of O2. I think I
may be misunderstood. And, if you follow my analogy, the candle and the
person will eventually suffocate (eachother/itself). The key in the room
analogy would be to find a plant that grows rapidly enough to sustain both
the candle and the person indefinitely. In an aquarium, the key is to feed
just the right amount. The way I look at it, the macronutrients are the
easiest to control so they are the best choices for the limiting reagent. 

> IMO, that's why it may make sense to use excess biological 
> filtration in a heavily stocked tank, but not in one that is 
> heavily planted and lightly stocked.  In this case, commensurately 
> large water changes will have to be done frequently to limit the 
> build up of nitrate.

	I agree.

>   If you _never_ see any measureable nitrate in your tank, odds 
> are that the tank is at least slightly nitrogen limited.

	Right. I agree again, but being right on the verge of limitation
and abundance is our goal. Better to be slightly on the limiting side if
you want to control your algae growth. 

AMC - in Atlanta where I am blessed with as-close-to replenished RO water as 
you can get from a tap! 8)