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[APD] RE: allelopathy

> I tend to think allelopathy is the most likely explanation as well.

I don't, neither do most Aquatic Botanist.
Considering the review editor of the journal Aquatic Botany is one of my
professors, and two other professors are on the board, naw...
I'd say bark up another tree, I've already discussed what I've seen and
what they think.

> My personal theory is that plants, when provided everything they want in
> abundance, greatly ramp up the production of allelopathic compounds. They
> create such a flood of such compounds that they are effective even with
> water changes.

But we simply do not see this in the aquatic enviorment.
If we concentrate the plant or algae chemicals that seem like likely
candidates and treat algae with these, sure, this will reduce some algae
But in the tank or in nature, there's not enough to even come close to
making any effect.
Nor are concentrated pulps anything like real world situations.

Some good examples are with grass land type plants, eg Bromus sp etc, drier
climates etc.
But nothing short of subtle at best has been found in FW systems.
The main competition that plants have over algae in FW: light. 
> This would explain why in a less-successful tank you can see concurrent
> plant growth and algae growth. The plants aren't able to produce enough
> allelopathic compounds to stop the algae. Once you ramp up the plant
> nutrients, they flood the water with algaecide and that's the end of that.

But all you have to do to test this theory: add carbon which will remove
the alleopathioc chemicals quite handily.
This is what they use in terrestrial studies as well to remove certain
regions around roots etc for controls some time or other test where they
want to remove the allelopathic chemical of interest.

Also, few plants actually produce these, othet these, why do we see almost
every plant when grown well, is able to illict the SAME EFFECT???????
All, 200 species of plants produce this same or similar chemical?
Even plants that normally live away from water in lotic systems(flowing
streams/rivers etc)?
What good is all that chemical then?
Huge expense, little gain.

> It also explains why the Walstad method works over the long term. The
> plants aren't producing the allelopathic compounds nearly as fast, but
> have much more time to accumulate because of the lack of water changes.

I don't think that's why it works.
I think it's simply stepped down, the rate is slow enough where the plants
and the fish are able to supply the needed balance to promote good plant

> I'd love to hear other explanations, but this is the only reason I can
> up with for why algae fail among an abundance of nutrients.
> - Jim Seidman

I think algae are preprogramed to live in specific environments, plants as
well but if they have enough nutrients relative to the lighting, they will
do well if you have enough plants to start off with. 
I also believe that algae/plants compete fiercly for NH4 produced in the
water column.
It's a much greater gain for algae to get the NH4 as opposed to NO3.
Plants also but not nearly as much. 
When the plants have good conditions, they likely remove all the NH4 as
fast as it's produced.
When the plants wane due to nutrient deficicencies, this uptake rate slows
down and the algae have a free meal.

Tom Barr

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