For a Salt DIP:
4 Tablespoon (1 Tbsp per gallon for a live in bath) of Aquarium salt per 1 gallon of water. (make sure the salt is dissolved and even dispersed in the water before adding the fish)
Have the water be atleast 78 degrees 80 is preferred.
Leave the fish in no longer then 10 minutes..but watch him carefully the entire time.
If the fish appears to be rolling over on it's side (passing out) it's time to take him out. Place him in fresh tank water and you should see him immediantly perk right back up.
You can do this up to 3 times per day, or just once a day..depending on how bad the fin rot is.
I always make a gallon up and use about 2-4 cups at a time (so the fish has room to swim around a little bit) if I have a fish with significant fin rot..as I know I'm gonna have to use the dip numerous times.
***************
The Collodial silver is gonna be the best bet..but from what I hear it's hard to find in the higher ppm's that you really need (I've heard you want atleast 50ppm). The IAL (Indian Almond Leaf) is easier to find but you usually have to order it. you can get a really good deal at
MajesticBettas.com . That's where I got mine and she will hook you up right. Her leaves are HUGE and she gives you extras. 1 HUGE leaf will last you a good while....I'd venture to say 1 leaf will treat 17 1 gallon tanks for a month (you can leave the leaf in there for a while (Ive left one in for a month at a time) and you can re-use them over and over until they stop making the water turn yellowish brown (liek tea) or they get slimey..if you re-dry them you can re-use them even longer..keeps them from getting slimey).
The tetracylcene you can get at your LFS or LPS..it's a common pennecillian based antibiotic..it's probably among the most mild versions...IMHO it's the best to start off with and then if you need stronger..go from there (no need to bring out the big guns unless you really need them imo).