See the APD clip below

"Elaine T" wrote in message
om...
Richard Sexton wrote:
In article ,
Robert Flory wrote:

"Elaine T" wrote in message
news:vlmId.13778 The red colors on your plants are from the light
intensity. That's one

of the really fun results of high light intensity and good amounts of
iron. Spot algae is one that likes high light intensity, which is why
you're seeing it now. I'd actually try dropping the nitrate rather than
increasing because you have a lot of fish in the tank, but don't drop
the K.


Actually the reds may be a sign of nitrate deficiency, or so I recall
seeing


Absolutely. Add nitrates and plants become more green. But red plants are
always red,
this isn't going to turn them all green, just a bit less red.

Conversly you can redden up your plants for a picture by restricting
nitrate.


Interesting. There's a sound biological reason for what I said.
http://www.sciencenews.org/articles/20021026/bob8.asp explains it. Bright
light causing anthocyanin production in plants has been well documented.
Basically anthocyanins are reddish pigments that help protect a plant's
photosynthetic mechanism from being burned out by too much light.

Reddish aquarium plants like Hygrophila polysperma "sunset", Rotala
indica, Rotala macrantha, Ludwigia spp., and many Crypts and swords do not
display their reddish colors under inadequate light. It takes a lot of
light for anthocyanin production to come into full swing, thus my reaction
that the red was due to high lighting.

Does anyone know the physiological explanation for reddening due to
nitrate deficiency?

--
__ Elaine T __
__' http://eethomp.com/fish.html '__

by Thomas Barr tcbiii/earthlink.net
Date: Sun, 13 Jan 2002
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.

Yep.

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
3ppm).

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.

This method gives the best color I've seen. But some plants respond
negatively to low NO3.

***Or*** is it that respond negatively to low NH4?
The NO3/NH4 dynamic cannot be ignored if we seek to understand and use this.
If the tank has a high enough snail, fish, shrimp etc population it will
increase the NH4 perhaps even to the point where little or certainly less
NO3 is needed.



In fact, the
macrandra went blood-red, but of course the leaf size was stunted from
lack of NO3.

I got great color at higher NO3(10ppm) and high PO4(1ppm). Could be the
harder water. We got the same lights, CO2, K+, test kits, etc. I also got
this in Marin. I recall it did not like the (too)low NO3 in the no fish
shrimp tank but did better out front with the higher fish load. Kinda wonder
how much of the NH4 vs NO3 is responsible. Well, that's the next question
now that we have somewhat of a handle on color

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

And hopefully not a middle aged pace A beach run with a soccer ball sounds
like order of the day for myself.
Regards,
Tom Barr