Caecilians sold as "rubber eels" are usually one of two species: T. natans or T. compressicauda. Both are fairly easy to keep in an aquatic set-up, and are generally happiest when they have a lot of hiding areas such as PVC pipe, and some type of platform to haul out onto on occasion. Most of them also enjoy floating plants that allow them to rest near the surface.
As Ed mentions, they're accomplished escape artists, and you want to prevent even the smallest opening, or any way for them to get leverage to be able to push against the tank lid. You also want to avoid filters that have intake attachments (such as the screen "baskets" that come with many off-the-back box filter intakes), as the animals are adept at removing these and getting their heads stuck inside either the attachment or the open intake.
I prefer to minimize tank decor and substrate, since rubber eels can be quite messy (but fun to watch) eaters. They have a habit of grabbing food items and going into a kind of "death roll", which often results in the item being torn up, leaving little bits that are a pain to clean up if you have highly decorated aquaria. They also love to burrow when they can, so tend to uproot plants and generally wreak havoc on decorative set-ups.
Rubber eels are easy to feed, and will devour a variety of worms, shrimp, and sinking pellet food. They're usually too slow to catch fish though, but if you house them with fish, avoid those with spines like corys, since caecilians will eat dead ones and get them lodged in their throat. They can bite, but it's more surprising than painful, and usually a result of animals that have been conditioned to be hand-fed.
Also, be warned that WC rubber eels were made illegal to import and own in Ontario (and possibly the rest of Canada) some time ago, so make absolutely certain that your supplier is dealing in CB animals. Even then, imported CB specimens are often confiscated, though there is a Canadian initiative to maintain captive domestic propagation.