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algea growth

I have been following the algae discussion and wondering exactly why 
high-nutrient/CO2 injected tanks are algae free (in the hands of people 
who know what they are doing). The results speak for themselves to some 
extent of course - but it isn't clear to me why the algae should die 
back just because the plants are happy. I find the low-nutrient argument 
much more intuitive - something like "plants have roots and can store 
more nutrients so they tolerate low nutrients in the water column better 
than algae" - that makes sense. But if there are plenty of macros and 
micros and light and CO2 etc etc, what holds the algae back? I like the 
allelochemicals argument - but then (as others - meaning Mr. Tom Barr if 
I remember right - have argued) big water changes should allow a spurt 
in algae production by lowering allelochemical concentrations - which 
doesn't seem to happen. It would also make sense to me to argue that by 
keeping background algea populations low with manual removal and algae 
eaters there isn't the potential there for a major population explosion. 
No one would dispute that this is true - would they? - but it doesn't 
explain the cases where simply adding nutrients makes problem algae go away.

I guess you could ask similar questions about regular roadside weeds - 
do weeds take over in poor soil because they really _like_ poor soil, or 
are they just filling in where other plants can't make it? So you 
fertilize the roadside and a bigger variety of plants will grow and the 
weeds will go away (or seem like less of a problem)? Hmm. Probably true. 
But do algea and plants compete directly for the same resources in the 
same way that different varieties of plants do?

I've been enjoying the discussions on this list very much - I've been 
following silently for a year or so. I have a particular interest in 
algae because I have a green water problem that I've knocked back from 
pea soup to a persistent but more transparent haze over the past few 
months - I'll spare everyone the details of the things I have tried - 
all of them suggestions from this list. I'm sure they are all good 
suggestions but I have a hard time following them consistently. When I 
try to starve my algae (you laugh?) I'm defeated by the junky substrate 
I put together when I didn't know any better. I have a hard time 
following the high-nutrient regime because I'm nervous that I'll be back 
to pea soup if I overdo it. I would also like to have a better 
understanding of why it is supposed to work....

I look forward very much to hearing your thoughts on this.