Yeah, BBA can be a *&^%$. I have heard recently that olive nerite snails will eat it. Can't confirm that. The only place I know to get them is AZ gardens.
Something else to try is Seachem Flourish Excell. Note, Flourish Excell, not plain Flourish. On any thick, well established BBA, spot treat it. Read the package for a daily dose for your tank and triple it. Use a 5 ml plastic dropper, usually can find them at the drug store in the baby meds aisle.
Turn off all filters, powerheads, anything that moves water. Wait a minute for the water to stop moving and slowly squirt the Excell directly on the BBA. It is clear, but thicker than the water so if you look close you can see it. Keep slowly squirting the BBA till you have used up todays dose.
Wait 2 minutes for the algae to absorb the Excell and turn everything back on. Where the Excell gets directly on the algae, it will die. It will take a few days to a week, but it will start to turn a reddish brown in a few days.
So every day do the same thing and treat a new area. Eventually you will have killed the majority of the BBA. Then continue adding a double or triple dose everyday for at least 2 weeks. This should clobber the nasty stuff.
I have seen adding Excell to the tanks usually kills new growth that is not established, but the big patches need spot treatment. One nice thing, after the BBA starts to die, usually a few days, then my shrimp and sometimes ottos will start grazing on it.
For filters, decor, etc that you can remove from the tank, you can kill the BBA imediately with bleach. In a big bucket add one cup bleach per gallon of water. I recomend rubber gloves. Even dilute, the bleach will be nasty on the skin. Dunk what you want to clean and wait. In a minute or so ....the BBA starts to turn light. It is now dead. Wait a bit longer and it turn almost clear. That is the satisfing part.
Now carefully rinse the bleaced whatever, and put in a another bucket with water and a lot of dechlorinator. I use Prime and a 5 times normal dose. This will neutralize the rest of the chlorine bleach. Rinse once more and sniff. All trace of bleach should be gone. Unless you did not wear gloves, then your hands will smell like bleach. For some time. lol
Sorry this reply was so long. I wanted to try and get it all in one shot. lol
HTH and Good Luck!!!!
Jeff