I'm going to leave this with...

For all you said, what you haven't answered is the riddle,
other than to say "wrong". Ok, well, maybe we collectively
are, that's fine...

But, if, as you say, higher plants need so very much more of
"everything" v. algae, just to survive, and all of that must
be in the water at all times, else our higher plants are
just dead beyond redemption... then...

How is it anyone, ever, controls algae? Shouldn't it simply
explode, killing everyone, and everything?

Something must be limiting them. You seem to propose
nothing, other than the mear physical presence of healthy
plants. Surely algae do not inspect their environment,
approve the health, state, and quantity, of the higher
plants, and give up.

(Aside - some higher plants to emit various biocides. Let's
assume our swords do not. Further, reefs and silk plant
tanks are known to exist w/o higher plants at all, yet are
also subject to acute, resolvable, algae infections.)

People have gone from no apparent infection, to acute
infection, and back. I have, even somewhat routinely on my
reef tanks. If, as you seem to claim, all higher plants
must fail before nutrients can limit the algae, then what IS
doing the limiting? Something is allowing routine
reclamation of all these obviously inoculated tanks? (and
not everyone is pumping their tank full of anti-biotics,
particularly on the reef side.)

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wrote:
Principal causes of

BGA has plenty of NO3, NH4 available in a tank if you have fish waste,
some plant decay etc, you have plenty iof Nitrogen for this species.

What you do NOT have is enough NO3 for the plants.

BGA and most other algae appear when something runs out, rather than
somethuing becoming excessive.

When something runs out relative to plants. BGA need next to nothing
to do quite well wereas the plants need far more.

Adding more PO4 is not going to encourage algae if there's enough
plant biomass that's growing, it's going to encourage plant, not algae
growth.
So when something runs out, lack of something, this harms the plants,
not the algae.

You pick the nutrient and the plants will always have a higher
requirement than the BGA for both growth and maintenance with FW
algae.
You are not going to limit iron either, plants leech out more than