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RE: [AGA Member] Cyanobacteria and Redfield ratio
Hi,
Is there any paper/research/reasoning to back this N:P 16:1 ratio?
Or is it totally empirical at this stage?
BTW, I read in several other sources that the ratio should be 10:1.
Of course the original Sears & Collins PMDD paper talks about avoiding N=0. Is the reasoning here the same - I mean - if your N:P << 10 then you are too damn close to N=0 where plants are starving and cyno can still produce N. And if so - if N=0.16 ppm and PO4 = 0.01 ppm.... - are we still OK??? :-)
Aviel.
-----Original Message-----
From: owner-aga-member@thekrib.com [mailto:owner-aga-member@thekrib.com] On Behalf Of Daniel Larsson
Sent: Tuesday, March 30, 2004 11:37 AM
To: aga-member@thekrib.com
Subject: [AGA Member] Cyanobacteria and Redfield ratio
> Date: Mon, 29 Mar 2004 12:37:23 -0500
> From: "Steve" <steve_wilsonii@fishpalace.org>
> Subject: Re: [AGA Member] Bacterial algea?
>
> My experience has been such that my planted tanks
> were always infested with BGA off and on. I would
> constanly be adding erithromycin to kill it and it
> would stay away for about a month. Test readings
> showed slight traces of PO4 and no traces of any
> nitrogen source.
This is my experience also. Too much PO4 in relation
to NO3. The plants strips the NO3, which becomes
limiting to the plants which stops the PO4-uptake
and the Cyanobacteria have everything it need because
it can use N2 (gas). Total domination.
The main reason to why Cyanobacteria can be confusing
is that there exists quite a few different Cyanobacteria and
some of these will forms colonies (sheets) where some of
the cells develops to heterocysts - N2 (gas) fixating cells.
This phenomenon is actually used by rice paddies in Asia
to get a natural fertilizer (dead Cyanobacteria).
Keeping the Redfield-N:P-ratio is really effective
against Cyanobacateria:
http://www.xs4all.nl/~buddendo/aquarium/redfield_eng.htm
Therefore the old-school tip "just leave it be and it
will dissapear" works - dead Cyanobacteria pushes
the N:P-ratio to the Redfield-ratio as they accumulate
and percipitates in the gravel.
A neat trick would be to bury the slime in the gravel instead
of vacuuming it out, where the slime dies and pushes
the N:P-ratio to the Redfield-ratio.
// Daniel
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