If you plan on having worms be the primary food source for a fire eel, this is the best way to go. I couldn't believe how much mine would eat and always be hungry for more. There are a number of places online that will ship you red wigglers in the mail. You just need a starter batch and give them some time to get established and they will start breeding in large volumes. You need a large semi-sealed bin that doesn't get too hot or cold or too wet or too dry. I kept mine in the basement and fed primarily oats and occasional fruit/vegetable. I would also mix in some flake fish food in order to include some vitamins. I found the trickiest part was keeping the right level of moisture, but the worms bred like mad.
It's been a while, so I don't recall which vendor I bought my starter batch from but a simple Google search will return several to consider (Uncle Jims, Speedy Worm, etc). They all include instructions for keeping/breeding as well. It's really easy if you have the right spot and set up for it. Just don't underestimate how huge fire eels get and how much they eat.