Ive always kept betta plus(stress coat) in my water, and i gave his tank a good scrub, soap free of course. I used baking soda to scrub real good and rinsed for like a half an hour with hot hot hot water. Then I filled it with cold water, added the betta plus, waited 3 hours for it to come to perfect room temp, floated him in it, added a new round of bettafix to it, and let him swim. It's basically all I can do until I can get to the Pet Store for a stronger med or the salt...
Just noticed the fin rot, but it's not bad yet, so I hope to nip it in the bud... dont need any more than one illness at a time
Will keep posted
Megs