Swordtails are a livebearing aquarium fish named for the sharp looking "sword" that the males develop as part of their tails. While olive green in the wild, these fish have been bred to provide a range of interesting colors, including yellow, red and patterned.
These aquarium fish live in freshwater and are relatively easy to care for. They mix well with other breeds, since they are quite tranquil. The female gives birth to live young which are fairly large and which can swim immediately. The fry can hide from larger fish and will eat flakes almost immediately.
Caring for your swordtails is not difficult. They like strong currents and will frequently jump over the surface of the water. You'll need about 50 liters of water per fish, since they enjoy plenty of space and do not do well with overcrowding. Ensure they have plenty of aquarium plants to hide in, as well. They adapt well to new conditions, making these fish a good choice for adding to an existing aquarium.
Livetails will eat flakes, small pellets and frozen worms, but they really need variety in their food. They require green foods, containing algae, in order to thrive. This can be provided by allowing some algae growth in the tank for the fish to feed on.
It's a good idea to limit these fish to just one male per tank, since they can be territorial. They reproduce easily, so expect plenty of smaller fish if you choose to house both genders in the same tank.
Overall, swordtails are fairly easy to look after and make great tropical fish for those just getting into aquariums. Treat them well and they should live for 3-4 years.