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[APD] Re: The why of the Barr method

Jeff Ludwig writes:
"Why can't we isolate this chemical, bottle it and make millions?  The
market for a chemical like this is enormous (almost all of it outside of
the aquarium industry).  Same comments apply to Jim's reply, if these
chemicals existed they would be commercially available already and this
would not be an academic pursuit. :)"

Well, there are a number of identified plant chemicals that have strong
anti-algae properties. That doesn't mean they're easy to bottle. You'd
either have to extract them or figure out how to synthesize them. Even if
you could do all that, it might not be cost effective for, say, preventing
algae growth in pools or lakes. For many applications copper sulfate works
just fine.

As to other's comments that you couldn't possibly have allelopathy with 50%
weekly water changes: why not? It's not as if there's no buildup in the
water. Just before the water change you'll have two weeks' worth of the
plants' chemical output. Even right after the water change you'll still
have one week's worth. If plants are really cranking because of the high
nutrient conditions, this could be enough. Some plants really pump out
chemicals under normal conditions. I'm not aware of any research measuring
the levels under well-supplemented conditions, but I'd expect them to be
significantly higher.

As to RUBISCO, I could certainly see how high oxygen content could
interfere with algal metabolism. But that doesn't explain algae inhibition
in Walstad-style tanks, which have much lower oxygen levels. However, maybe
the infrequent water changes really help the allelopathy.

Perhaps there are completely different methods of algae inhibition in
Walstad-style and CO2-enriched tanks, but allelopathy could explain the
effects in both.

- Jim Seidman

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