Red Swordtail

1 Red Swordtail Species Profile

The Red Swordtail, also known as the Red Xiphophorus, has a natural body color of pale blue-green. Its biggest feature is the sword-like tail; females have no sword. It is a common and indispensable aquarium fish, easy to keep.

Chinese name: Red Swordtail

Kingdom: Animalia

Class: Osteichthyes

Family: Xiphiidae

Also known as: Swordfish

Phylum: Chordata

Order: Perciformes

Genus: Xiphias

Binomial: Xiphias gladius

Chinese scientific name: Red Swordtail

2 Red Swordtail Appearance

The Red Swordtail is mainly from Mexico and Guatemala. Through breeding, its color now varies—besides red, also white and blue. It is easy to keep and robust.

The original length was 10 to 12 cm, but in captivity it is smaller, about 7 to 8 cm. The body is spindle-shaped, like a moonfish, but with a longer caudal peduncle; the dorsal fin is central, pelvic ventral. The hallmark is the male’s lower caudal lobe extended like a sword, sometimes exceeding body length, hence the name. The natural form is pale blue-green. The male’s lower caudal edge extends into a needle-like ray (the ‘sword’); females have none. The swordtail is an indispensable aquarium fish. Breeding has enriched colors—red, white, blue, etc. Representative forms: red sword, green sword, white sword, black-fin red sword, black-fin white sword, and mixed sword.

3 Red Swordtail Habitat and Care

Easy to keep and fairly gentle, so it can be kept with other gentle tropical fish.

Very adaptable; grows and breeds at 20 to 25 C in weakly acidic, neutral, or slightly alkaline water; best 24 to 26 C, tolerating 5 C briefly. Omnivorous, eats all foods. Although ‘armed,’ it is not aggressive—gentle and never bullies the weak or other species, easy to mix. When startled it jumps strongly, so add a lid for safety.

It can breed in concrete ponds. Place guppy grass; parents hide and spawn; after birth, net the fry out separately. Being large, it births every 30 to 50 days; large males can produce over 200 fry per brood; newborns hide on plant leaves. At 3 months the male’s sword starts to develop.

4 Red Swordtail Feeding

What to feed is a common concern; many refuse food when environment changes, so scientific feeding for healthy growth matters.

Use professional fish food, but bread crumbs also work, since it is not picky—a plus. When breeding, do not keep same-brood stock beyond two generations to avoid inbreeding degeneration.

Newly bought fish, after adapting half a day, can be fed when they start pecking at the glass or substrate sand.