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Re: [APD] Allelopathy was Re: pearling after water changes Vol 2

Liz Wilhite wrote:
> Yeah, it is but it's role in aquaria is hotly debated. Walstad cites a
> number of papers in her book and attributes the lack of algae in her tanks
> to allelopathy -- she recommends no water changes.  Tom has posted a number
> of references -- quite a long number of them -- to this list that contradict
> the references Walstad cites. There is an article about allelopathy in
> planted aquaria on the Tropica website, written by Ole Pedersen if I recall
> correctly, that supports the idea that allelopathy has a limited role at
> best in aquaria.  I think that is Tom's conclusion as well.

It stands to reason that if plants can release enough allelopathic 
chemicals to affect other plants in virtually unlimited volumes of water 
that those chemicals would have even greater effect in the confines of 
the aquarium. Of course, that conclusions assumes some things not least 
of which is that the aquarium environment doesn't cause plants to reduce 
or halt their release of allelopathic chemicals.

> My personal belief -- and that is all it is at this point -- is that Tom is
> correct about exposure to CO2 gas making a big difference in growth but I
> haven't seen anything yet that really indicates that is true with one
> exception.  I've noticed that when the first bit of panted, submerged water
> sprite reaches the top of the tank that the growth of the entire plant is
> much, much faster than when the entire plant is submerged.  I see that in
> water sprite growing in both CO2 and Excel tanks.  I also observed a change
> in growth rate when I rescaped the CO2 inject tank and moved the water
> sprite from a place where CO2 bubbles were blown onto the plant to the one
> spot in the tank that has no bubbles.

Let me preface this with my confession that I have no opinion yet on 
whether exposure to gaseous CO2 is beneficial/neutral/detrimental to 
aquatic plants in planted aquaria. That being said, having a water 
sprite located where CO2 bubbles were being blown into it suggests that 
it was closer to the CO2 outlet than it was after having been moved to 
where there were no CO2 bubbles. Aside from the bubbles, could there 
have been a CO2 concentration difference that would explain the observed 

I'm not just skeptical of this whole phenomena's postulated cause, but 
of everything in general until I have eliminated the other plausible 
explanations to my own satisfaction.

"He who throws dirt is sure to lose ground."

Jerry Baker
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