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bga battle

The theory about DOC's and the effect of H2O2 which Jeff posted is
interesting (APD # 618).  At the same time I treated my tank with Maracyn
(APD #617) a friend of mine, who was reluctant to use it, treated a similar
outbreak with Kent's Poly-Ox, which is a permanganate based oxidizing agent.
With one dose, at the recommended amount, he achieved about a 90% kill of
the bacteria within one day, with NO cloudiness and no effect on water
chemistry, etc. I suspect the action of hydrogen peroxide and permanganate
are the same--they are oxidizing "something" in the water which is retarding
the growth of bga.  It's conceivable that they are oxidizing the bacteria
themselves, but it seems more likely that they ore oxidizing a nutrient (for
if in fact the bacteria were "oxidized" one would think that other
biological systems in the  tank would be affected).

I discussed the above and my other adventures with my son, and he gave me
the following information which I think might interest the group (he was
also commenting on my observation of post-erythomycin cloudiness which I
reported in APD #617):

"......about the tank.  i read your posted message, and it is a good summary
of what's going on.  i would say that the cloudiness you saw was most likely
the result of the death of cyanobacteria.  if the bga disappears, its
remnants must go somewhere, and the description of the water that you gave
me fits the lysed bacteria theory.  and one more thing - you asked where the
"green" went.  there is no reason to think that lysing green bacteria would
cause the water to turn green.  if you take a test tube filled with a
suspended bacteria that appears clear and add a bacteriocidal agent, that
water will turn brownish.  the final appearance of that liquid is not, as
far as i know, directly related to the color of that bacteria.  so from my
lab experience, i would say that there is no reason to think that lysed bga
would appear green in solution.

i was reading about cyanobacteria and i found two things you might find
interesting.  first of all, i read that certain types of this bacteria
thrive under conditions of low oxygen.  apparently, at higher oxygen
concentrations, cyanobacteria's nitrogenase (nitrogenase is the enzyme that
converts N2 to ammonia) is inhibited.  have you ever tested the oxygen
levels in your tank?  of course, if the erythro solved the problem, there's
no need to worry about it.  but if the stuff ever comes back, you might want
to check out your O2 levels.  while looking at your fish (and your plants)
makes me think that your water is sufficiently oxygenated, i don't know what
the level of "low oxygen" is in the context of these bacteria.

another thing - you keep saying that "you can't treat these bacteria with
good water quality".  you were referring, i think, to the fact that your
ammonia, nitrates, and nitrates were very low and that your pH and hardness
and all that were good.  there might be a reason why your excellent water
quality might actually promote the growth of cyanobacteria.  according to
what i read, cyanobacteria are generally not found in environments where the
supply of fixed nitrogen (i.e., ammonia) is ample.  however, they "form
quickly if the fixed nitrogen becomes limiting".  your tank fits the
description of this latter environment.  with low fixed nitrogen levels due
to nitrogen fixation by your filter bed bacteria (which you have tested and
shown to be low), it appears that cyanobacteria would be induced to
proliferate. that might explain why your nitrogen levels were looking great
but that bacteria kept coming back so quickly.

i found this stuff out looking at a textbook ......"

These findings fit very well with the DOC theory.  Low oxygen levels again
would not be conducive to oxidation of DOC's while high oxygen levels would
be.  I also fits with other observations that bga growth seems regionalized
in certain environments (like my tank) and that it grows in areas of low
water circulation.  The nitrogen observations are interesting also, although
I'm not sure that "fixed nitrogen" (in context) doesn't refer to ammonia,
nitrite and nitrate, rather than just ammonia alone.

Rob Sirota
Huntingdon Valley, Pa.