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Re: Love the Algae confusion

Sean wrote:

>I just got done reading the "Love the Algae" article in PAM2 and need
>someone to clear up something for me or maybe explain it differently.
>     Brad Metz writes, "Like plants, algae can only grow as fast as the
>limiting resource allows."
>     How does one know what the limiting resource would be and what does
>this really mean for the "control" of excess algae?  Especially in a
>young (1-3 month) setup??
>     Sorry to bring up a very deeply discussed topic but I am trying to
>learn as much as I can and understand aquatic gardening BASICS.
>     I have read all I can read about algae in The Krib and on many
>other related websites...it gets overwhelming and confusing for a new
>plant hobbyist.

The author is likely referring to the "law of the minimum" or the
"principle of limiting factors" attributed to the German agricultural
chemist, Liebig. It can be stated something like this:  Unless the plant is
growing as fast as it is capable of growing, given optimum amounts of
everything it needs as well as optiumm temperature, then its growth will be
limited by whatever requirement is in the least supply.  Requirements can
be the various mineral nutrients, CO2, light, and water.  What the law
means is that if you don't increase the limiting requirement, but try
increasing other requirements, the plant wont grow any better.  In other
words, if phosphorous is limiting growth, increasing nitrogen or light, or
CO2, or any other nutrient, won't help the plant very much.  This principle
should not be regarded as absolute.  If Phosphorus is limiting growth, and
nitrogen is close to limiting, also, but not quite as much as phosphorus,
increasing nitrogen will increase growth a little bit, but not as much as
it would if the plant had plenty of phosphorus.  You would get the best
increase in growth by adding phosphorus.

In keeping down the algae in aquaria, the idea is to have some nutrient,
usually phosphorus, very low, so that the algae doesn't grow very much.
Hopefully, the higher aquatic plants---the ones you want---have a better
ability to take up phosphorus than the algae does so that they can still
grow.   With some kinds of algae, the plants can compete effectively for


Dave Gauthier wrote:
>I am currently building a new hood for my 90 gal, and I have left some
>room underneath for night-viewing lights.  I have a few questions...
>1) Has anyone used night-viewing lights on their planted tanks, and if so,
>were there any adverse effects on the plants?
>2) I have seen both red night viewing lights and blue (actinic) "moon"
>lights advertised.  For my purposes, blue light would be more
>aesthetically appealing, but I also know that many fish are not sensitive
>to red wavelengths, thus the popularity of red night bulbs.  Am I going to
>keep my fish "up" all night with a blue bulb, or will this do a reasonable
>job of simulating moonlight?
>FYI, I'm not planning on putting too much red/blue light over the tank.
>Just one 48" T-8 (anyone know of good sources for these in red or blue?)
>or a pair of 13W CFs from AH Supply.
>Dave Gauthier

There are some plants that need a dark period for normal growth.  I have
seen this requirement in members of the genus Hygrophila.  If kept in
continuous light, the new leaves will be distorted, small, and they will
not have any mesophyll region containing air between upper and lower
epidermis.  Thus, they will look dark green, like leaves of Eigeria densa
(Elodea, Anacharis).  Even dim lighting overnight will cause this distorted
growth.  You can always tell if the LFS keeps its tank lights on overnight
by the appearance of Hygrophila.

Paul Krombholz, in bone dry central Mississippi