OK It looks like this thread is pretty much dead, and I came too late to see anything Tom/plantbrain wrote. I am sorry I missed that. But I'll add a couple comments anyway. Art asked us to play sea cucumber in the beginning of the thread, and I took the bait.
Art, I understood the reason in starting the thread, and you asked a simple and specific question- but I could accuse you of trolling in your own space! (j/k!)
I believe most of you are exactly right; and that it's a combination
of nutrient/light competition, and allelopathy. Simple and/or complex, on either end.
I mean allelopathy in a broad sense, which to me may include oxygen levels/redox potentials, where locally regulated by the higher plants, or other "universal" higher plant processes I wouldn't guess at. Complex chemical algicides wouldn't necessarily be the only 'true' allelopathy. Yes, that's fuzzy, overlapping simple competition, but that's how I see it. Interactions overlapping interreactions on a continuum, not anywhere near simple discrete one-cause one-effect systems. I've been out of the hobby for several years, so can't use EI and PPS as specific examples, only maybe as a means of forcibly tipping complex series, or networks, of balances. Oxygen, and maybe peroxidase difference (was that brought up here?), is just the easier example for me.
I said "regulated by the higher plants", because obviously the algae and cyanobacteria are doing the same thing at the metabolic/photosynthetic levels: Redfishbluefish's post (#104) reminds me that chloroplasts (and such) in all organisms are really all various cyanobacteria, evolved as endo-symbionts, as we are symbiotic with our mitochondria*. The biggest difference would seem to me to be sheer mass- it only takes a few higher plants to equal the dry bulk of a tank overgrown with most kinds of algae.
The spirited discussion would be because of each person's variably unilateral approach, weighing one or few parameters as 'the important'. I'm sure it won't be an eternal argument, just insufficient data for now, as mentioned several times already.
* No matter how factual, natural, and logical, it still seems a feels a little creepy thinking about how my minute-by-minute survival, and very existence as a species, is completely under the control of a bacterium in my cells that I am fundamentally unrelated to. Kind of makes the strict idea of Linnaean Kingdoms melt down in my head too. More continuum. In the fourth grade, I read a series of books by by Madeline L'Engle, including A Wind In The Door, involving sentient mitochondria and "farandolae". It influenced and scarred me for life.
And, Pessimist (or skeptic):
Art Giancola wrote:
I remember Kaspar Horst of Dupla thought that Kraus' oxygen theory had been disproved.
Andrew Cribb wrote:
If there was one magic component (such as your suggestion of oxygen) responsible for slowing or stopping algae growing, it would have been found before now by better equipped researchers.
The best funded research specifically for aquarium
environments would be supported by major aquarium supply companies. If I were CEO, and one of my research teams found that magic bullet, I would lock it up unless or until I could get a profitable product or system out of it, which couldn't very quickly or easily go DIY. Extend that thought however you see fit. Although the explosion of peroxide use probably impacted some algicide sales, I am again not only referring to oxygen, it's just the example quoted.
Redfishbluefish: I don't have an answer on your hornwort question, and haven't grown any in a long time. It was most useful to me to combat diatoms, rather than algaes, possibly through sequestering silicates. But your post reminded me of the whole symbiosis thing. I think I need to have a talk with my endosymbionts, and make sure we're in full accord, before I go to sleep!
Thanks for letting me ramble. My mind has been stagnating the past several weeks, it's outgassing now.