Black Swordtail Facts

Background

• The scientific name for swordtail fish is Xiphohorus helleri. Black swordtail fish are a subspecies of the olive and red-striped swordtail fish. They derive their name from the black pigment found on their bodies and "tails." However, the name swordtail is a bit of a misnomer, because the "tail" on a black swordtail fish isn't actually a tail; it's a male reproductive organ termed the gonopodium. Female swordtail fish don't possess this organ, and hence don't appear to have tails.

Habitat

• Wild Swordtail fish are native to Central American waters. When domesticated, these fish require large tanks filled with warm water between 78 and 80 degrees Fahrenheit. While a single black swordtail fish can live in a tank as small as 2.5 gallons, a 10-gallon tank is ideal. Pairs of these fish require at least a 15-gallon tank. The tank needs a proper mineral content including sodium, potassium, and magnesium, as well as a strong, secure lid, because these fish love to jump.

Color

• Although it adds to the fish's beauty, the black pigmentation on black swordtails is actually cancerous. People sometimes breed these fish hoping to obtain an all black swordtail, but when improperly done, the black pigmentation often turns into tumors that lead to death. Black swordtails aren't meant to be entirely black; they should have clear or colorful fins. To obtain the perfect black coloration and avoid cancer, crossbreed black swordtail fish with non-black swordtail fish through multiple generations.

Reproduction

• After black swordtails mate, the female can store the sperm in her body and repeatedly give birth, month after month. You'll know if your fish is pregnant because the female fish's belly swells up and changes color. Black swordtail fish also don't lay eggs; instead, they give live births. After a fry is born, the mother or fry must be moved to a separate tank or the mother will eat the fry.

Diet

• Wild black swordtail fish are omnivores. They eat algae, insects, worms, and virtually any food source they come across. Domesticated black swordtail fish can live off fish flakes and survive on a primarily vegetarian diet, as long as it includes high-quality plant matter. They do need meat incorporated into their diets, especially during gestation. During this period, they need plenty of meat, such as shrimp and bloodworms, to give birth to healthy young.