I have been having a really terrible time keeping Bettas. I have lost count on how many I have lost in the last 9 months. The male I have now I have been able to bring back from the dead 3 times now. The last time was a very severe case of ich.
I bought a female from the LFS and put her in the divided 5g tank with my boy. A few days later I noticed a few spots on the female and within 24 hr the male was in serious respiratory distress although showed no obvious white spots. I started with upping the temp to 80 F and quinine sulfate that I use on all my other fish. Things seemed to deteriorate very rapidly, so I did a 100% wc and tried Jungle Ich Clear and they seemed to react even worse to that. Another 100% wc and tried another treatment with same results. Now the poor male was just rolling around on the bottom gasping. So I tried going back to the simplest treatment- 85 F and added a tablespoon of salt to 5 gallons. 24 hrs later he was still in bad shape but he was mostly upright. Over the next 3-4 days I almost gave up but he started showing signs of improvement.
Now 3-4 weeks later they are both happy little piglets. If I don't feed fast enough they will jump and take the food from my finger. The female jumped the divider and beat the living tar out of the poor boy and he had literally no fins left. It has been a week or so and he is growing his fins back quite nicely and all I am doing is 50% wc weekly.
the simplest methods work the best.