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Re: po4

About the article at this link:

I'm not sure that a lot of useful conclusions can be
drawn from the experiment described in the article. 
Iron is added to an area with high nitrogen, and an
increase in "primary production" is observed. 
Conclusion?  That iron was a limiting factor.  But
there was no control.  What if phosphates had been

Also, I am not sure what they mean by the threshhold
amounts of N and P that algae require.  Does it mean
that when you have reached those levels you should
have lots of algae?  Or just detectable algae?  How
were those numbers derived?

"it is extremely doubtful that nitrogen and phosphorus
are at such low levels in aquaria that they limit or
prevent the growth of algae."  Do they imply that
there is no utility to keeping your N and P at low
levels?  What if your N and P double?  Triple?  Should
you be already above threshhold values, will it make a
difference?  I believe so.

The article implies that the greater body of
literature supports phosphorous as the most important
limiting factor in freshwater.  In fact, my old
biology textbook (that predates Sears-Conlin) states
"If the phosphorus concentration of a lake increases,
an explosive increase in the density of photosythetic
organisms may occur."  It also cites an experiment: 
"The far basin of this lake was separated from the
near basin by a plastic curtain and fertilized with
carbon, nitrogen, and phosphorus.  Within two months,
the far basin was covered with an algal bloom, as can
be seen in this photo.  The near basin, which was
treated with only carbon and nitrogen, remained

What we lack are rigorous experiments.  Or even
semi-rigorous.  Our tools of measurement (test kits)
are crude.  To be more accurate in experiments, we
should setup fishless tanks (no fish food),
reconstituted water, and strictly controlled inputs,
with control tanks under the exact same conditions as
the experimental tank.

One interesting phenomenon that I have observed in my
own tanks is that algae when moved to an algae-free
tank usually dies quickly.  What makes this so?  I
could benefit from better record keeping (my dog
actually ripped apart my old notebook, hence my
reluctance to start after losing months of data).

Enough rambling.  Just a call for science.  More of
it.  And more art too.  :)


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