The incredibly beautiful Sailfin Tetra is only sometimes encountered in the trade, despite being a truly unusual and beautiful fish. This is due, in no small part, to the fact that they're really not attractive as juveniles, the size most commonly offered for sale. However, as they mature, the fins of the male will extend, earning this fish its name. There appears to be several different geographical variants, and possibly different species, though they're all currently known as C. spilurus.
Interestingly, these tetras behave more like cichlids than tetras. Males will often battle with each other, though damage is rare. They will guard small territories, which usually include a cave, such as a coconut shell, an overturned flowerpot, or the like. The males will flash their fins at females, and frequently spawn in these caves. Like cichlids, the male will guard the brood, and fry predation is rare.
Sailfin Tetras are not the best fish for a community aquarium, as they can be shy. One can think of these like an Apistogramma, and maintain them in an aquarium with small, unassuming tetras, Corydoras, Loricariids, or even Apistos and other dwarf cichlids, but they should not be used as a dither fish.