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Cyano Preliminary Results/long
Adam Novitt posted a note about the results of his survey of green water
tanks. I participated in the survey and looked forward to the
collection of this information. I hate to be negative, but I think the
information presented and particularly the comments, are essentially
useless. What we have here is mostly misinformation and uninformed
First and foremost, green water and cyanobacteria are completely
different animals. <G> What we refer to as green water is not bacteria
at all, but unicellular algae. Karen pointed this out last week,
apparently to no avail. Speculating about an increase in bacteria over
the summer isn't even germane to the discussion. If in fact we are
discussing cyano, we can throw the whole survey out because most of us
thought we were reporting on green water.
Having encountered both problems on occasion, I can say that they have
occurred under completely different conditions. I have never had cyano
and green water problems concurrently. For one thing, cyano can occur
in well-run, low nutrient tanks with crystal clear water, particularly
between the gravel and the glass, as has been frequently reported on the
Regarding a cure, Adam writes, "[N]othing works and everything does."
So much for "research." We know that a complete darkening of the tank
for 4 or 5 days after a water change reliably cures most green water.
We also know that mechanical filtering below the size of unicellular
algae will always cure green water. We know that one can kill green
water with sterilization. We also reasonably suspect that nutrient
balancing and limiting excess nutrients will prevent long term green
water problems. Green water is not inherent in planted aquariums. We
have also had some very interesting speculation about the possible role
of nitrogen limitation in connection with green water. To say we know
nothing about curing green water is far from accurate.
Adam talks about "new tank syndrome." I think we're fairly close to
reaching agreement that there is no such thing in our planted aquariums.
We have poor nutrient balance during run-in resulting in excess
nutrients, or we can restrict nutrients initially, and slowly increase
them as the plants take hold and start growing. If a lot of people
report green water during early tank run-in, my guess is that over
fertilization and excess nutrients play a role.
Regarding water conditions, Adam writes, "All can apply, from hard to
soft, basic to alkaline and pure to polluted." One thing I can say with
certainty is that 18 megohm lab grade water from my RO/DI unit will not
support green water growth. It takes nutrients to grow plants,
Sorry to be so negative, but I'm hoping we can advance the hobby and not
throw ourselves into confusion with this sort of exercise.
Regards, Steve Dixon in San Francisco