Salt baths aren't always the cure for fin rot but they are good for mild cases, usually if you see a hole or some fraying at the ends. But if your case is more severe where he has lost a large portion of his tail, you should consider medication. Although using salt baths throughout the duration of the treatment is still beneficial, not all Betta fish like salt baths, so it's in your judgment whether to use them or not.
If your case is more severe, you should first address whether or not your betta fish has fungal or bacterial fin rot. Fungal will have a tendency to eat up your betta fish's tail in a consistent manner and might appear as a white fuzzy bit at the edge of their fins, while bacterial will attack their fins in random areas leaving the edge black or bloody.
It is important to correctly assess the infection according to situation; as dramaqueen said use Jungle Fungus Eliminator in the case of fungal fin rot, and I would recommend Maracyn-two for bacterial fin rot. The use of a hospital tank is also a good idea, but your 1 gallon fish bowl is good enough :) Anything bigger will be a hassle, since you will have to do frequent water changes through out the course of their treatment because you don't want your fish to be reinfected with its dirty water (plus ammonia and nitrite from your fish's wastes will stress your fish out, making its immune system weaker).
If you are completely unsure which one your fish may have, you may use Maracyn (aimed towards fungal infections) and Maracyn-two (aimed towards bacterial infections) in combination, but do keep in mind the dosage you are giving to your fish, because you CAN overdose your fish.
Follow all the medical instructions, and if you haven't seen an improvement after two weeks of treatment, I'd recommend switching to ampicillin (Geltek Ampicillin is a good choice, and if you can't find ampicillin, you may use penicillin, but Ampicillin is the preferred choice.). The reason for this is because you don't want to jump straight to heavier medication because the bacteria can develop resistance to it and medication can be quite stressful for fish.
When your fin rot is gone, than you may use BettaFix. BettaFix isn't actually a treatment for fin rot, but it's rather meant to help promote regrowth after the fin rot is gone.
And in the case where you've had to do prolong treatment, you may have to do frequent water changes for the rest of their lives since they may be more prone to have relapses because their immunity to the disease is lower.
Also, keep the tank at a steady 80degrees F because it will promote better health for you betta fish and help its immune system combat the disease.
Phew :'D I think I'm done. I figured I'd give you all the fin rot info I know, since everyone was just giving you just the tip of the iceberg.
Last edited by BakaMandy; 09-14-2009 at 02:51 PM.