Thank you, Tom and Philosophos, for your responses.
I didn't get a firm answer to my question, "Why does good CO2 retard the growth of BBA and other algaes?" because, apparently, there is none. (In fact there doesn't seem to be any scientific data to support that claim that CO2 does that.)
I'd say response time.
Algae have a much better response time to CO2 varaition/adaptation when the CO2 ppm's change, than plants even might.
So large variations will select for algae, not plants.
There's is strong evidence for adaptation and Rubisco with CO2 change. This is expensive metabolically for plants and central to everything in terms of uptake.
With carbon, they cannot make anything.
Algae, might simply sense this CO2 variation.
They use CO2 as well, and when it's easy to get for a brief time even, they can respond much faster over short time periods. In other words, algae spores, germination, might be signaled by CO2 changes over short time frames
That would suggest both why plants grow poorly, thus provide a substrate for algal growth, and why algae grow during this phase. Both observations are found in aquariums, perhaps natural systems as well.
If you think about CO2 as nutrient, like NH4, or PO4 etc...........then it makes more sense.
However, it's still speculation/correlation.
I can induce algae easily, every single time with simply fooling with my CO2.
Does that imply direct cause and why I stated above?
Many aquarist are tempted to say so.
I have seen that several hypothesis have been offered to explain this effect (if it actually exists) but that none have been subject to controlled experiments, because of the difficulty in doing that.
Even though a lot of the postings here have a scientific bent, we still learn a lot from observations and experiences even if they are unproven.
Philosophos, watch out - that "A" virus spreads.
I think the thing that gets me wondering, it really has to do with ruling things out step wise that we can rule out.
The metric for that(falsification) is much lower than than finding cause/s. So now we have fewer and fewer variables to look at, or.....we are a much closer to the truth than we where say 15 years ago.
I think looking at specific algae, specific plants etc, and really good measurement of light, nutrients(fairly easy for an aquarium, but also really look at temp again. CO2 and O2 have been on my mine for the last few years obviously.
Correlation is very high and other alternatives are few with CO2 variation.
It also explains algae in non CO2 and CO2 aquariums, and testing it is harder than any other parameter in our aquarium.
A data logging CO2 meter/probe is required to get a good consensus.
Here's an example from the 1600 Gallon tank over 24 hours after it stabilized and curiously, all the algae died off after a couple of weeks and the tank has done extremely well since:
The other thing, there are plenty of clowns on the web blow hards, etc...............willing to speculate all day, some will even look up a few papers for support. But very few are willing to test, detail out the question, the issues, and then set up and do the test.
They just wanna yell louder than you to make their point and convince every one or anyone willing to listen they are right. They are extremely rarely willing to test anything critically. I see plenty of clowns doing this, and have to wonder how they know the "cause/s" without measuring anything, without testing CO2 critically, without telling me anything about their methods to get there, rational, and why there's no things they falsified and ruled out along the way(very curious about that one!!!) etc.
Diana Walstad is passionate about some things and has done nice test, she spent some $$$ to do it and have some analysis done. There are some speculations that she cannot/has not/will not do, for the sake of $, time etc.
Very few bother doing non CO2 these days. Testing even less so.
But what we both do adds up....and that of others that have come before and after us. I am interested in the non CO2, CO2 issue.
I think it links algae issues.
And we have to look at both to come up with a reasoned cause for algae in the context of CO2/non CO2 in planted tanks, because both get algae and both can be algae free.
Blow hards on the web claiming they know the cure to algae and why always use CO2/Excel. Almost never have seen they use non CO2 methods.
So that's often forgotten(cough cough, overlooked is more like it) in their discussions.
You cannot do that.