Well guys....did you sort out the BBA issue?
I am currently the proud owner of another BBA tank. Some may remember that one of my tanks cracked last year and I had to move all inhabitants to another, overstocking it in the process. Two months down the line BBA started growing in the tank. The tank had never had any algae since I set it up a few years back so from my point of view, I have no doubts what the trigger is, excessive bioload. The BBA is most prominent under the spraybars. There's BBA growing out the spraybar holes and I have a crinum calamistratum planted right under the flow, with leaves as long as half the tank, and they are all bba covered. The opposite side of the tank is not as affected. So BBA needs "food" to trigger it and high flow to flourish. I've both in that tank, lots of fish and lots of filtration and flow.
I think we should start seeing a tank as a whole, not just as a bunch of plants that need co2 and nutrients. I presume you all keep fish in your tanks and you feed your fish so I'd look into the bioload as a whole and what could be triggering high bioload which the tank is unable to cope with.
I am pretty confident that when I reduce the bioload the BBA in that tank will die off.
I believe I sorted out the BBA issue in my previous tank by reducing the bioload. I had ran the tank overstocked for years and weeks after I removed a bunch of fish to another tank, the BBA stopped growing completely within weeks!....after having it for a long time...
And I also caused it in my small tank last year when overfeeding a bunch of fry and a baby clown loach. Once I removed the fry and started feeding a lot less, the diatoms, cyano, green algae on the glass and eventually BBA mass outbreak died off completely. The rampant algae outbreak was so bad that it destroyed the plants almost completely. I was admiring the crypt leaves, first covered in diatoms to the point of looking dark brown, with cyano overtaking on top of the diatoms, and BBA on all outer edges, as much as I could see through a brown/green coated glass....That's how they looked in the end. But the fact is, the appearance and disappearance of algae got nothing to do with co2, light or lack of nutrients or damaged plants in my case(s). Once I removed the fry and stocked with just a few fish to keep the filters going, all forms of algae stopped appearing. The plants took a good while to regrow but they did without any further input and without any algae. The BBA seems persistent only in overstocked tanks in which the root cause for high bioload isn't removed.
Out of curiosity, would those that battle BBA state the size of tanks, amount and types of fish they keep, the type and amount of food given to the fish? Perhaps we can establish a connection. Perhaps Andy is right about B12 and heterotrophic bacteria as a root cause following high organic load.
If you want an experiment that will yield results, setup a planted tank. Stock it with a good bunch of fry, e.g. guppy fry will do. Feed them as fry should be fed several times a day with high protein food. Do daily water changes if you want. Do this for at least 2 months. You'll get yourselves a lovely algae outbreak and BBA will follow eventually, perhaps after other hints like persistent diatoms.
Show me one overstocked tank that hasn't got BBA eventually providing the overstocking is maintained. I'd be very curious to know how the owner managed it because each overstocked tank I ran got BBA early or later.