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Re: Aquatic Plants Digest V2 #1123

Subject: Re: Nutrient limitation

>Nitrogen is the single most common element in the atmosphere.  It will be
>almost four times more common in the water column than oxygen, because of the
>forces that cause exchange of gases at the surface.

But that doesn't affect the situation in the tank as far as plants are
concerned.  Palnts can't use atmospheric nitrogen except for the very few
(like legumes and Azolla) that have a symbiotic relationship with nitrogen
fixing cyanobacteria.  When we tale about useable nitrogen in the aquarium,
we're talking about ammonia(um), nitrite and nitrate.  

Otherwise, we'd _never_ have to supplement nitrogen in the planted tank!<g>


Subject: ere: nitrifying bacteria

>Karen wrote:
>> Nitrifying bacteria colonize substrates.  They are not free floating.

Cynthia wrote:

>AFAIK this is incorrect.   Nitrifiying bacteria are ubiquitous in aquaria;
>on the substrate, ornaments, plants and in the water.  

I don't believe this is correct.  Ornaments and plants _are_ substrates for
nitrifying bacteria.  Someone correct me if I'm wrong, but my understanding
is that they are _not_ free floating in the water column.  Otherwise, it
would not make any difference how much or how little surface area a
bacterial filter had.  That's what makes fluidized bed filters so
efficient... they have a _tremendous_ amount of surface area.

Karen Randall
Aquatic Gardeners Association