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The red color thing

Tom Barr wrote:

> Well the red color thing we started on a few years ago surely 
> shows some trends there.  Higher NO3 more green and faster 
> growth in many(most) species.  Lower NO3 redder colors.
> PO4 stress also can produce redder colors.  Higher P to lower 
> N ratio helps also in many species.

Tom, at the risk of opening this thread again (and you know it's been
running on the Sfbaaps list for years), I thought we found that red
coloration was stimulated by stressing, limiting **either** N or P in
the presense of an adaquate supply of K and the other nutrient.  

In other words, running relatively high NO3 and strict limitation of P
with the occasional PO4 "pulse" produced large, luscius red leaves in R.
macrandra (I should note here that IME macrandra is sensitive to N and
doesn't thrive in environments with more than about 10ppm or less than

Reversing the proportions had a similar effect: relatively high PO4
(above 2.0ppm!) and less than 1ppm of NO3 forced just about everything
else in my aquarium that could turn red to do so.  In fact, the
macrandra went blood-red, but of course the leaf size was stunted from
lack of NO3.

Michael Rubin in San Francisco, where it looks like a good day for a
middle-aged run ~