I'm sorry you lost it. When Amy posted pics of her eel it looked like an Aeromonas sp. yours looked like Columnaris. At any rate Sulfa drugs are an effective treatment against either at a Ph over 7. Furan 2 is better at a Ph under 7 how ever there is an over lap of about 6.8 to 7.2. This is somthing to remember going forwrd, Furan 2 is better topically for Aeromonas while Kanamycin is absorbed and generally more effective for Columnaris, and since these bacterial infections are often hard to differentiate by the naked eye this can be an effective combination when unsure. It is also not uncommon for Columnaris to be confused as a fungal infection and is sometimes misdiagnosed in the early stages. Kanamycin can also be combined with Furan 2 and/or Metronidazole for a combination parasitic, fungal, & bacterial infection treatment. But I don't generally like useing a "shotgun" approch unless all other options have been exhausted.
I'm very sorry you lost your fish. Is the tank currently empty? If so You might want to tear it down clean it with bleach and water and start over. You will need to get a declor to nutralize any residual chlorine when done, I know you use don't need it currently. Again I'm very sorry and wish I could have been of more help to you.