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Re: Nutrient limitation

>Date: Fri, 12 Dec 1997 08:27:18 -0500
>From: Bjorn Straube <straube at digital_net>
>> Date: Wed, 10 Dec 1997 15:19:27 -0600
>> From: "David W. Webb" <dwebb at ti_com>
>> I've found that cyanobacteria do contribute organic nitrogen to the
>> The process involves the cyanobacteria rapidly consuming nutrients until
>> they become nutrient limited in some way other than nitrogen.  At this
>> point, they begin to die off and decay, contributing their nutrients
>> to the system.
>But this is not nitrogen "Fixing", they are not pulling in nitrogen that
>comes from outside the system (what a horrible thought ;)).  They only
>give up nitrogen that was avalible within the aquarium to begin with,
>they just "got there first".

Actually, I'm assuming that nitrogen fixation is occuring.  Cyanophytes are
known to fix atmospheric nitrogen in low O2 situations.  Many cyanobacteria
growths occur in low O2 locations.  Although I cannot prove that nitrogen
fixation is occuring, that's what I think is happening.  My cyanobacteria
plague last summer was due to nitrogen starvation and subsequent melting of
my anubias.  I don't think the cyanophytes had enough nitrogen available to
produce the mass of blue-green algae that I wound up with in the tank.

Karen mentioned removing all dead or dying plant material from tanks.  I
run ultra-low maintenance tanks now because I flat-out can't afford to put
much time into them.  I rarely remove anything from my tanks except during
water changes.  
I have pruned live plants from my system, removing nutrients, and when I
had a severe cyanobacteria plague at one point, I did remove some of it by
hand, but I mainly let the snails take care of it once I made the
conditions less suitable for cyanobacteria.

David W. Webb 
Going to re-plant my zero-maintenence 20g this weekend (first tank set up
in my new house after the move).