Biofiltration/plant/bacteria and Ammonia

[James Folsom <hymy at arches_uga.edu>]

>
>
>1) The concept of plants "getting to NH4 before nitrifying bacteria" is a
>little bogus, IMHO. Plants don't chase after NH4 any more than bacteria do.
>NH4 from fish and decomposition diffuses into the water and is available to
>all takers equally. Water movement helps distribute it. A molecule of NH4
>will be consumed by whatever consumer it comes in conact with. I would
>venture a guess that bacteria, in general, have a better chance of consuming
>NH4 than plants because there are more bacteria and they are everywhere.
>

I would like to add something to this:

1) I would guess that the uptake of ammonia is concentration dependant. 
 Plants having a different optimal concentration than bacteria.  Ammonia 
is present at almost undetectable levels (if not zero) in aquariums. 
 This leads to the assumption that any that is produced is utilized by 
something almost immediatly.  Thus which ever organism in the tank has a 
higher affinity for ammonia at near zero concentrations will consume all 
or most of it.  I would guess that plants  only utilize ammonia when 
there is an ammonia spike.   The bacteria probably get it it the rest of 
the time.

2) A further wrinkle in this is the fact that ammonia that is not 
produced by fish urinary excretions is produced within biofilms that are 
attached to surface/water interfaces.  These biofilms are complex 
communities, each member contributing something to the others.  Ammonia 
produced from solid waste is in close proximity to other bacteria which 
use it to produce nitrite, and other members of the community use the 
nitrite to produce the nitrate that is released into the water column. 
 Its like an assembly line in a way.  This is why cylcling takes so long 
in a non-planted tanks, it takes time for the community to form.   This 
also relates to why those bacteria supplements don't work so good.  If 
if you add a bunch of all  the bacteria types only the ammonia producers 
and the ammonia users will thrive at first.  The remainders will suffer 
until there is enough of a colony producing nitrite.  If you add gravel, 
mulm or colonized filter media from an established tank, then you are 
adding functional communities of bacteria, and good results follow.

In conlusion ammonia from decomposition is unlikely to be readily 
available in the tank because of bacterial community action.