Now, Bio 1, not even 101, teaches... "A Species will
proliferate unless, or until, it encounters a limiting
factor". A proper biological argument, surely any regarding
population control, is framed in terms of what "limits" that
species, and that species directly.

But that is in an _ideal_ situation in order to show the concept, not
to be applied without consideration of many other variables.

There are few macrophyte periphyton competition studies.
This is not Bio 101.

I gave several mechanisms that do in fact limit growth in an aquarium
algae.
Not just one. It also works in non CO2 plants tanks and marine planted
tanks to some extent.

This issue has been discussed several years ago on the APD in depth
and still here and there but no one contends that excess PO4 causes
algae. Paul Sears was part of that discussion, one of the authors of
the paer that you have referenced to.

There are also many exmaples of folks telling how well their plants
grow by adding PO4.

You have not supported your contentions, I have.
The proof is in the pudding, why don't I have algae like you seem to
want to claim?

Magic water?
Crystal powers?

When you do otherwise,
you open wider and wider ranges of potential causality.

Actually I have proven quite definitively that excess PO4 that is
available for both plants and algae equally, not not cause algal
blooms in planted tanks with good plant biomass, CO2, moderate-high
light, good dosing of the other nutrients.

If you want to talk about causual mechanisms, you need to be able to
isolate the issues and deal with PO4 in a controlled manner.
In order to say x causes y, you need to make certain that the other
parameters are not influencing your results.

Steve Dixon and I were some of the first people to do this in planted
tank context regarding PO4. I also showed that NH4, not PO4 or NO3
caused Green water and staghorn algae blooms in FW planted tanks.

Algae/BGA exists. If, as you claim, higher plants are
limiting, they are doing it through bio-chemistry.

Higher plants are limiting the algae?
I do not think they do it through alleopathy, you can add activated
carbon to the filter to remove any organic compounds that cause
allelopathy.

Also, look up the APD and other sites.

Name the
link.

?

We know it is resolvable, routinely, in various
media, without nutrient starvation of the higher organisms.

Some higher organism have different niches than smaller ones.

Resolution/limitation (in tank) rarely depends on
predation,

True but it can tip the scales in a few cases, it's not something I
rely on.

need not depend on antibiotic toxicity, and can
be accomplished regardless of lighting levels.

Regardless of lighting levels? You sure you want to say that?

Whine all
you want about PO4 "ain't it", Fe "ain't it", XYZ "ain't
it", but until you form a proper biological argument,

Oh, I most certainly have spelled it out quite well and better than
those before me.

spelling out what factors ARE "it", I'll go with the
nutrient limitation, thank you.

Uhm, I did in the last post, I gave multiple plausible causes.
You can believe want you want, you are still wrong.
Research shows this, I can show this in a plant tank, you can show
this to yourself in a planted tank.
The AGA contest winners, all the plant clubs have got it all wrong and
you are the only that's right?

Humm you might want to actually try it and see about this, maybe read
some of the references, ask around.

Hey, you can believe what you want to believe, but your still wrong
about PO4.
That does not change.
You have not supported your own arguements with a single reference
beside Paul and Kevin's.

Lighting is surely limiting, less light less stuff,

Depends, if light is limiting, then yes, but this is not always the
case.
Aquatic Plants generally are better competitors than algae for light.
Call up Dr. Bowes, the guy's studied aquatic plants and algae for 30+
years.
Ask.

but silk
plant tanks still do end up infected so "low light" is
hardly the complete answer.

I never said it was "complete".

You want a complete answer in aquatic plant-algae dynamics here?:-)

Temp is limiting, range
depending on species, but does the range 68-80 matter to
"our" species?

Not too much.

Redox seems implicated, but a well lit,
reasonably clean, plant tank tends to maintain a serviceable
redox on it's own, and I've had BGA at high redox in my reefs.

I did not say redox, but you could argue high O2 levels cause many
species of algae, BGA etc to photorespire causing large losses, up to
40-50% of the fixed carbon.

Reef tanks and plant marine tanks are different. Careful not to
compare apples and oranges, same thing goes for Northern deep minimal
littoral zone lakes used to make assumptions about planted tanks vs a
shallow warm water tropical lake packed full of aquatic macrophytes.

One is much more applicable to the questions at hand with planted
tanks.

Regardless, we all control light, temp, and less so redox as
a matter of routine. BGA/Algae comes and goes.

Mine does not come and go.
I have not had it become an issue in a decade or more.

It must be
resolving because 1) something in the water is killing it;

Well, carbon will remove organic causes, water changes also will
reduce the effects, it cannot be nutrients since we have added the
nutrients the BGa needs to live to excess.

or 2) it is failing to find something else it needs (nutrients).

Maybe it knows something else is growing, much like a seed that will
not germinate due to other plants surrounding it or until a fire comes
along and disturbs it.

Before you reply back, I'd suggest you look up and ask around about
this issue that we limit algae through PO4 or Fe limitation.

The observations all over the world and the winners in many contest
directly conflict with what you are saying, not to mention past
research.

Regards,
Tom Barr