I think there are several reasons for low algae presence at moderate
non
limiting nutrients with macrophytes.

Perhaps it is nutrient limitation but what type?
NH4 seems to cause blooms but NO3 does not to nearly the same degree.
So teasing apart which form of nitrogen might be the key.

PR(Photorespiration) may cause some of algae basal cells to release on
plant leaves(but my
own study with CO2/O2 levels were inconclusive, algae did well on all
gas
conditions, high O2, high CO2/O2, high CO2 only and the control). Both
algae and plants respond well to high O2 and both prefer CO2 over
HCO3.
Water changes always seem to help. Removes many epiphytic algae and
any
that are floating around(see Zimba and Hopson, roughly 80% of the
epiphytes
were removed by swirling in water in a flask for 90sec).
We scrub, prune old leaves that get infected. Some folks fluff the
plants to get any detrital matter that settles, often algae.

We add herbivores.

Some suggest allelopathy, but all 300 species of plants elicit the
same
response? What is the likelyhood that all 300 species have the same
strong
chemical and effect? Extremely small.

It has to be something more general and I see this occur in non CO2
planted
tanks as well and in nature.

I've suggested that algae know "when someone else is home." and don't
bloom. When the plant growth is sour, the NH4 uptake declines,
bacteria
don't have enough time to respond, algae gets a free meal of NH4 even
if a
slight increase, this means a lot more relatively to a small algae
than a
larger plant.
O2 levels decline as since the plant production rate is declining
also.
Bacteria may also rob algae of any trace amounts of NH4 due to the
higher O2 levels from healthy growing plants.

This is the best idea thus far:

Algae spores may not have any signal like = NH4 presence telling them
to
grow(plants remove all the NH4 when they are healthy, bacterial
removal also occurs rapidly when the O2 levels are higher).
So very low/absent NH4 may tell algae that someone else is there.

This idea would make sense in general terms and also explain why good
plants growth = poor algae growth even if there are nutrients
available
for vegetative growth.
I've observed that many algae just stop growing when placed into a
tank
that has good plant growth and also with tanks that had poor plant
growth,
got some algae, and then stopped growing after the plant health
improved.

Another two stage pathway:
High O2 levels may activate bacteria in the substrate that suppress
algal
spores that are generally present in the substrate much like a seed
bank/reservior. This may co-occur with the plant's uptake of NH4 and
these two may be linked.
I did not test for this as I used no substrate in the original test
with
high O2/CO2 etc.

The nutrient levels are great for plants, they out pace and out grow
algae
when feed a stable diet, algae are better able to deal with dramatic
changes while it takes much more time for plants to get established.
You
can see this in shallow lake ecology where macrophytes are removed or
as
they fill in. It takes years for them to redominate again. It does not
take
long for the algae to take over.

Shallow lakes are very prone to wind resuspension of nutrients from
the
sediments. This allows a bloom of algae since it suspends NH4(and
other
nutrients)
Macrophytes reduce wave action and prevent resuspension and this leads
to
gin clear water. There is some arguement with this theory but it seems
correct to me from what I've read about resuspension.

We do this when we replant and rework the tank, doing a water change
right
takes care of this.

This issue has not been explore much in the literature, mainly
phytoplankton vs macrophytes and not a lot there, the pickings are
slim for
periphyton/epiphytes vs macrophytes in the context that is useful for
planted aquarist.

It has to be something general.
I think it has a lot to do with algae's signaling to bloom or stay put
till
things get ripe again like with NH4.

Everything I've done with NH4 tells me it's the problem in natural
ecosystems and in planted tanks, SW or FW.
Many bothersome algae bloom readily with NH4 additions.
But they don't if you add NO3+the other nutrients.
You can try this by adding more and more fish to a thriving healthy
tank.
Once you pass by the rate of NH4 uptake by those plants, you provide a
ripe
place for algae to grow. You can add everything else and not get a
response.

Plants and algae occupy different ecological habitats also. A small
amount
of NH4 means a lot to the algae vs the plant.

So that's the seed theory/notion idea that algae know when or when not
to
grow based on NH4 and why healthy plant growth = poor algae when
there are
enough nutrients for either group.

This seems like the best expaination so far. Now I need to test
this:-)
It's a combination of things but I think this is why the new algae
does not
grow. This is particularly noticable in many tanks and with any method
folks use.
This also applied to lakes and non CO2 planted tanks.

Non CO2 planted tanks also have this same pattern, they have low
inputs of
NH4 from fish food only and if there's enough plant biomass, there's
generally sufficent NH4 uptake. These tanks also have less light and
slower
growth of both the plants but importantly also the Algae.
CO2 is preferred by algae as well, but a fair number of plants will
use the
HCO3 and most all algae do or can. Some algae just need very little
CO2 in
their environment to do well.

So the algae grow slower in non CO2 planted tanks, they have plenty of
plants to remove the NH4, then growth rates are slow so the nutrients
demands can be met from fish waste and substrate uptake, cycling
resulting
in extremely low algae presence.

Since you do not resuspend the tank weekly with water changes, the
tank
does well/better without water changes. If you added CO2, that's fine
since
the higher growth rates in those tanks removes all the NH4
resuspended/leeched out at a faster rate than the non CO2 planted
tank.

Then if you apply this to a CO2 enriched low light tank, then you get
extremely low algae presence as well.If you keep adding more and more
fish to a planted tank, you will get algae and it's not due to NO3,
PO4, K+, it's due to NH4.

This theory seems applicable to all planted tank methods also. Even
some
lakes and streams.

Regards,
Tom Barr

Tom, most of what you wrote is well reasoned. Some points
I'd like to see expanded upon noted below...

wrote:

O2 levels decline as since the plant production rate is declining
also.

You might want to elaborate here. Yes, sick plants will
produce less O2. But, otherwise, most freshwater tanks are
at near saturation for O2. I won't say "all", but even
aggressive CO2 dosers who actively work to limit air/water
interface (a mistake IMHO) usually fall short of bringing O2
levels too far below saturation.

Are you working in the ranges of mild super-saturation?

Bacteria may also rob algae of any trace amounts of NH4 due to the
higher O2 levels from healthy growing plants.

This is the best idea thus far:

Algae spores may not have any signal like = NH4 presence telling them
to
grow(plants remove all the NH4 when they are healthy, bacterial
removal also occurs rapidly when the O2 levels are higher).
So very low/absent NH4 may tell algae that someone else is there.

Perhaps.

But you may have to navigate another issue here. Most
aquariums are 1) GROSSLY (orders of magnitude) over stocked
with well established bio-filter surface area; 2) exhibit
high flow rates through that bio-area; and 3) are near O2
saturation from their air/water interfaces.

High NH4 would seem a fairly extraordinary event. Inmate
death, sudden gross overfeeding, chemical induced death of
the bio-filter surfaces, etc. While algae seems a fairly
routine event, and is generally "present", if slowly
growing, in all tanks.

Another two stage pathway:
High O2 levels may activate bacteria in the substrate that suppress
algal
spores

Might spore/cells simply be sequestered in the bio-films? I
can enhance the spread of green spot by simply disturbing
the substrate. Liberated "bits" that land on various
surfaces, like (even healthy) plant leaves, seem to support
the sprouting of new algal spots.

that are generally present in the substrate much like a seed
bank/reservior.

I'm with you 100% here. Seed bank, POP, localized decay
(NH4), whatever, nothing good ever comes from particulates.

Shallow lakes are very prone to wind resuspension of nutrients from
the
sediments. This allows a bloom of algae since it suspends NH4(and
other
nutrients)
Macrophytes reduce wave action and prevent resuspension and this leads
to
gin clear water. There is some arguement with this theory but it seems
correct to me from what I've read about resuspension.

I'd like to see how you equate a shallow lake, with a few
feet of "muck" as substrate with a typical aquarium's few
inches of epoxy coated gravel. Or mine, with a couple of
inches of large river rock that stays 90% debris free and is
surely O2 saturated.

I can surely see how shallow lake processes can liberate
significant nutrient spikes, including NH4. I just need to
see the connection between the lake and why my aquarium
(with comparably no similar nutrient bank of a lake).

We do this when we replant and rework the tank, doing a water change
right
takes care of this.

Ok, let me explain my tank a bit. 2-3 inch water polished
"river rock" over egg crate. Much of the system's water
flow is from left to right, and remains under the egg crate
(underground river effect). On "intake" to the filter pump,
a valve splits the flow between the river and the overflow.
(creating an RUGF water flow through the rocks)

Obviously, I can trigger resuspension of debris tramped at
the rock-to-rock interfaces. But there are remarkably small
regions and remain highly oxygenated.

When I clean, I tap a percentage of the flow and "dust" the
debris, which due to differential flow, tend to be sucked
downwards into the "river". But - not all - and where those
stripped debris land, algae is likely to appear.

Yet I'm still left managing algae. If I mis-dose/over-dose
I can, and have, triggered outbreaks. I've never dosed NH4,
as that would be foolish.

Points I'd like to see more on, I guess.

- While I agree most gravels are a mess, it seems unlikely
that an undigested (NH4 source) nutrient sink exist in my tank.

- When particulate debris that are present are disturbed
(stripped of their bio-film prison?) they are aggressive
algal sources.

Everything I've done with NH4 tells me it's the problem in natural

I'll admit, as much as I'd like to test this POV, I just
don't the strength to dose NH4.

You can try this by adding more and more fish to a thriving healthy
tank.
Once you pass by the rate of NH4 uptake by those plants, you provide a
ripe

Or these truly massive bio-filters everyone seems to have?

Not that NH4 isn't a problem, for some. A friend has a, um,
swordtail collection packed into a 20G. Lives on a farm,
nitrate polluted well, grossly overstocked (like 20 full
grown 5-6" adults, lots of fry, a billion snails or so), he
grossly overfeeds, and is probably the first truly under
filtered tank I've ever seen. The silly thing also gets 1-3
hours day of direct sun.

A mess to view, to be sure (he can't bring himself to kill
anything). But, he shows continuous low levels of NH4. He
has trouble with green water, probably compounded by
bacterial bloom, and uses a diatom filter once a week. He
Does 50% changes a week. He maintains a stand of Anacharis
(in pots filled with garden dirt).

Has also has a few spots of green hair algae near his filter
(clear inoculation) - but it is completely non-expansive.

In this case, the tank must be limiting on P (he shows none
on my not-so-sensitive kit) or some other nutrient (besides
Fe - his well has to much).

Then if you apply this to a CO2 enriched low light tank, then you get
extremely low algae presence as well.If you keep adding more and more
fish to a planted tank, you will get algae and it's not due to NO3,
PO4, K+, it's due to NH4.

I'm not sure you can so easily make that association.

If you add more fish, you must feed them more. That will
surely produce more NH4 (for Carp, at least, the rule seems
to be, about 14% of the protein in their food will express
as NH4). It will also cause your bio-filter to quickly
accommodate the additional feed rate.

But, my can of Tetra shows "Min. Phosphorus 1.3%" as well.

*******************

Tom, Just came to mind, but you may need to address on more
observation regarding NH4.

LFS plant holding tanks are notoriously algae ridden
senss-pools (my apologies to those that maintain theirs, and
my personal condemnation goes out to my local PetSmart).

But, be all that as it may, a common trait of these
abominations is they are rarely connected to the livestock
circuit. Many have no substrate.

No fish to feed protein to, and very few, if any, aquatic
ferts use ammonium forms of N. Do they all secretly dose
Miracle Grow? I just don't know, maybe the do. One well
maintained plant-vendor I know doses PMDD - but won't
sell/recommend it for lack of profit (Hey, he has to pay the
rent).

Being stressed by their treck through the retail delivery
chain, I suspect the plants aren't very happy. They are
probably not taking in much of anything (or causing
limitation) N, P, K, or otherwise.

But, NH4 is probably the one thing that we know isn't in there.

************************
wrote:

Tom, Just came to mind, but you may need to address on more
observation regarding NH4.

LFS plant holding tanks are notoriously algae ridden
senss-pools (my apologies to those that maintain theirs, and
my personal condemnation goes out to my local PetSmart).

But, be all that as it may, a common trait of these
abominations is they are rarely connected to the livestock
circuit. Many have no substrate.

No fish to feed protein to, and very few, if any, aquatic
ferts use ammonium forms of N. Do they all secretly dose
Miracle Grow? I just don't know, maybe the do. One well
maintained plant-vendor I know doses PMDD - but won't
sell/recommend it for lack of profit (Hey, he has to pay the
rent).

Being stressed by their treck through the retail delivery
chain, I suspect the plants aren't very happy. They are
probably not taking in much of anything (or causing
limitation) N, P, K, or otherwise.

But, NH4 is probably the one thing that we know isn't in there.

************************
wrote: