Medications for aquarium fish can be somewhat expensive and esoteric, since there are multiple medications available for the same disease. Here are some that I've had success with:
Clout cures ick.
Tetracycline by the same people who make Maracyn cures fin rot.
TripleSulfa by Aquarium Pharmaceuticals cured the white body slime on my corydoras catfish.
Maracyn-Two cured the internal bacterial infection that a koi I bought from Wal-Mart had.
Maracyn cured the white body slime on the same koi.
Hope that helps someone.