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babar100 at ix_netcom.com

Dear David,

You seem to be having a similar problem to one I have
had since November.

A whole host of APD postings can be found in the
archives about green water, what may cause it, the
green vs. BG algae debate, and the use of flocculents.

Flocculents first:  If you have sensitive fish, especially
small tetras, I recommend against their use.  I tried
two different brands, and both kill fish, probably by
interfering with their osmoregulatory systems...don't
ask, I'm not a fish person.  This will happen if your
water has less than about 50ppm salts, which mine
does.  Someone on the APD mentioned that they'd
read this in the recent TFH (I believe it was that
magazine).  Why don't the products include a warning
like this on their bottle?
Also, the benefit of the flocculent seemed to fade with
time.  At first I got what looked like dramatic
improvement - cloudiness disappeared totally, only to
return in a form seemingly "resistant" to the flocculent.
 So, I quit using it in favor of diatom filtration when

Green algae vs BG algae:  Neil Frank convinced me
with his APD posts that BGs include species that are
free floating (I don't know about the little nodules you
noticed) and can look quite green, just like green algae
that cause green water.  This is important, because
the treatment for BGs and greens is so different!

All I know is, massive water changes, use of
flocculents, and reduction in nutrient additions did
NOTHING to remove the cloudiness for me.  This
suggested that the organism was a BG, some of
which can fix nitrogen, which you probably know.

A few weeks ago I started testing nitrate (which is
consistenly zero) and adding small amounts (1/2 tsp
at a time) of KNO3 ("stump remover" at any hardware
store).  This seems to be helping, confirming that BGs
are involved.  When things get even slightly cloudy, I
use a System 1 diatom filter which removes all of it. 
The diatomaceous earth becomes light green in a
couple of hours.

I don't have it licked yet, but the diatom filtration needs
to be done only twice a week now (down from every

Hope this helps.  Let me know if you have other

Roxanne Bittman