I bathe bettas in IAL rich water...like 4-5 leaves in a 2 gal hospital-spa tank for new rescues or sick fish.. usually the prior. I swear by it. The fumic acid harms fungus, bacteria and keeps parasites away. if you cant get any then try gathering some oak leaves if they are in your area.
here is a prime example of how fast and well it works...
the betta in this tank had NO rays left, on any fins. he was in a tank with giant gouramis. xD it took him 3 weeks to get to this and still growing.