Sorry for bumping an old thread but I have an update. It had been 8 days now since I quarantined my Betta. His tail has gotten gigantic, but his fin rot has not gone away. His tail has grown by at least a quarter of it's pervious size, and his lower fin has gotten twice as long. I have observed him, and he is not biting his tail or anything, and is back to being super hyper. But what is wrong with the tail? It keeps on getting longer, but the rips won't heal themselves.
During these past 8 days I have been switching him from one fish tank to another(1 gal and 0.75 gal) while changing water 100% daily. Also I have been adding aquarium salt and bettafix along with the conditioner.