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Green Water
Adam wrote: "I'd be happy to forward the folder to you regarding the
green water.
One thing I've got to say is that from my very unscientific survey there
is absolutely no reliable cure for Green Water. Some people do fight it
for months on end using magnum filters only to have it return in a
couple of days and numerous people have used the dark tank method to no
good end. Many did massive water changes to nil results. I think its
very safe to say that there is a great degree of variables here."
First let me say that my note read more harshly than was intended, as is
sometimes the case with email. I applaud the effort to learn something
about green water. It is a complex opponent. Let's keep at it a bit
and see what turns up. Why don't we set aside green water from gross
excess/imbalance of nutrients. It comes as no surprise that a wildly
out-of-control tank pitches up with a green water problem.
It's been my experience that once it gets going green water can hold on
for dear life pretty well. It can maintain itself in pretty good, even
very good, water conditions. I am one of those who could not eliminate
green water through massive water changes alone. And I worked at it
quite diligently for several months.
You mention that numerous people have tried darkening their tanks to no
avail. This is very interesting. I was only aware of Roxanne's recent
report. Could we get some more information on those efforts. Perhaps
Roxanne and others will provide some details.
1. Were the tanks kept in complete darkness? By this I mean, were
they covered completely with a dark blanket or some other means that
shut out the light entirely? (I used folded layers of a dark brown
blanket and duct tape to darken my tank completely when I used this
method successfully.) The reason I suspect this aspect is quite
important is the speculation by folks more knowledgeable than I that
unicellular algae "must" have regular access to light to live. A
related question: Were all sumps, trickle filters, canisters filters
and the like kept in complete darkness as well?
2. How long was the tank kept dark? 4.5 days worked for me. Karen
recommends at least 5 days if memory serves. The higher plants in my
tank were not noticeably affected by the period of darkness.
3. Were water changes performed before and after the period of
darkness to rid the tank of excess nutrients? A bunch of freshly killed
off unicellular algae might provide enough nutrients to kick off yet
another bout of green water.
4. Any data on post darkening water conditions, especially
macronutrients, would be helpful and might provide clues as to why the
effort didn't work.
If memory serves, Carlos Munoz has a pretty strong hunch that nitrogen
limitation plays a role in some green water problems. In my case once
the green water got going, maintaining nitrates at the 5 - 10 ppm range
didn't help the problem; nor did maintaining nitrates at the lowest
possible levels. How about others? I'm still intrigued with the idea
that nitrogen plays a role in this.
Regards, Steve Dixon