I see you give this advice over and over, but the fact that you won't even consider that there might be exceptional cases seems to be a bit too rigid of a mindset to me. I don't want CO2 in my low light tank, like I said, and the fact that you haven't seen something in 20 years doesn't mean it isn't true.
Respectfully, your advice didn't work for me and it's not clear to me that it's 'fact' that CO2 correlates so closely to algae.
Oh, I've more than considered exceptional cases.
I did in fact say there are other factors that lead to long term algae issues, current, filtration, general care, if you have some hypothesis you'd like to pose that says X causes BBA, I'm all ears.
Every single case I've addressed for myself and others in the last 20 years have all been, without a single exception, due to some type of CO2 issue.
We are talking well past 100 tanks.
I never said there are not exceptions.
Try messing with your CO2 and see if you get algae then. If you want it to happened even faster, add a lot of light. Drop checkers have many issues, if I used them and thought they were accurate, all my tanks would also have algae.
Yes, I'll get algae in tanks time to time. But I can beat them back pretty well. And I've gotten good enough to induce the algae and then go back and test to see if I can get rid of it. GDA is the only one I cannot induce easily. Most any other is pretty easy to do.
I think most assume they maxed their CO2 levels, they gas their fish. But they rarely go slow and progressive in small incremental adjustments, then carefully watch. Watch the plants and..the new algae growth. This is what I was telling Shineycard255.
Like most hobbyists, we are impatient.
If we adjust the cO2 slow and progressive, notch by notch on a good needle valve, make sure we have good current, clean the tank often, keep up on things routinely, use less, not more light, then algae is not much of threat.
A recent example:
1.2 W/gal of Tek T5's at 36" from the gloss. About 30 umols.
This is complete control over algae in such tanks.
Even with minimal plant biomass, eg, not just tanks full of stems.
Both tanks got a little BBA.
Typically about the 3-5th week in and both cases where due to........yep, CO2. The new growth stopped completely after careful tweaking.
But the old BBA? It stayed awhile.
I killed it with a big water change, sprayed the wood with excel, done.
In the larger Gloss tank, I have some BBA on the rocks, but it's never gone farther, and I've spot treated here and there, it's slowly dying off.
Older leaves the plant has given up on also get BBA.
After a big hack on my Starougyne lawn in my 180, the anemic whitish shaded leaves are suddenly exposed after trimming the tops.
Those leaves are not adapted to the high sudden light. The plant responds by not "defending them". A small amount of BBA covers a few leaves after 2-3 weeks till the new growth buries the BBA leaves and they decay away as new growth piles on.
In my 120 Gallon, there's a few short tufts of BBA on some spots of the wood that are below the water change line(roughly 70% in that tank).
The CO2 is obviously plenty good for any plant that's added in there, but BBA still will slowly grow. Why?
It cannot be due to the CO2, so I'd say there are exceptions also.
However, the BBA is so minor, it's hardly problematic, but it is there.
Nuisance algae where it causes real issues are/is due to CO2 however. I've yet to see otherwise. One might argue that new tank start ups are prone to BBA or other species more than any other tank, it might be due to new tank CO2 demand is not yet dialed in. But it could be due to something else.
I've fixed many friends, club members BBA issues and been hired to fix such issues. Some have taken a few years to figure out some things, some only a few days. Many try everything else, then finally after exhausting every other cure all, come back.
I was that guy myself.
Even then, I doubted for years and years.
Maybe I'm just lucky 100 out of 100 times?
Maybe, it's possible. But I've never relied much on luck.