why algae dont grow when plants do great

[Neil Frank <aquarian.subjects at mindspring_com>]

previously, the title was "Why plants grow and algae don't"

First, I still dont discount the allelochemical factor. This can help start
the demise of the algae

Tom wrote:
> Algae at high levels of CO2 photo respire.
>Normally this is not the case. This has something to do with dissolved
O2>>content also or may be indirect (say internal O2 vs external O2 levels).

Hmm.... When a plant contains a high concentration of oxygen this can pose
a problem for the normal photosynthetic process. As with many of Tom's
posts, I had to recall the meaning of the term. A nice graph can be found
at http://www.marietta.edu/~spilatrs/biol103/photolab/photresp.html

Tom may have touched on THE factor. I wonder if it is the O2 - the
supersaturated oxygen caused by the large number of plants in the confined
space of your tank -- that causes the demise of the algae.  Are the algae
or certain algae not capable of photosynthesizing under these conditions.
Sort of like the use of H2O2. Seems reasonable that many algae have not
adapted to live in such conditions. In a tank with pearling plants, there
is always less algae. Then extra nutrients are needed to keep this process
going.

this O2 effect may also be why Amano (at the convention) says you should
turn off CO2 a few hours before the lights go out. When O2 is satuarated,
vascular plant photosynthesis also stops/slows,..... but it doesnt kill them!

>Once inoculated, GW is hard to get rid of unless you use fine
>filtration(diatom/Micron), UV's, blackouts.

Green water, even a haze, attenuates light... reduces the intensity and
shifts the color (it looks green so it must absorb red and blue). This
makes it harder for the plants to produce as much O2. 

Neil
ISN'T THIS HOBBY GREAT!

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