I'm interested in this issue as well. I bought a betta from a breeder and it looked amazing. After 2 months, Angus' fins began to deteriorate. Tankmates were 5 harlequin rasboaras, 2 endlers, 2 dwarf banjo cats, a cory a mess of shrimp and a scarlet badis. Despite emptying the 15gl planted tank of other fish except for a cory, the fins continued to shred. I watched a mess of videos and read a bunch of info. I tried salt at triple the dose (the cory didn't seem harmed), no change in fins. I did almond leaves. The fins got worse. As a desperate measure, put Angus onto a cutting board, dabbed him with 3% hydrogen peroxide, put him in a 5gl bucket, dosed it with Maracyn 2 and did that for a week. I put him back in the tank about 3 weeks ago, but have been busy at work to pay much attention. His tankmates consist of 1 feeder guppy, 2 corys and shrimp. Only 1 thing changed that makes me wonder...I added a pothos. But I had washed its roots and I did put other pothos from that bunch into my other tanks. Anyway, my apologies for the long post, and I look forward to seeing how others respond.