Montezuma swordtail

Care at a glance

Overview

The Montezuma swordtail is a livebearer for a roomy community tank with hard, clean water. It is best with a little experience.

Caring for the Montezuma swordtail

Keep Montezuma swordtails as a small colony of about six to eight in a tank of 32 gal (120 L) or more. Mature males grow a long, horizontal sword off the tail, so they need more swimming room than the common swordtail, Xiphophorus hellerii. Use sand or a fine substrate, with plants around the edges and plenty of open water down the middle.

Run the water at 68 to 79°F (20 to 26°C) and aim for the cooler end, since they do best in well-oxygenated, subtropical-leaning conditions. Keep it hard and on the alkaline side, at a pH of 7.0 to 8.0, with good flow and steady oxygen. They have low tolerance for nitrate, so use strong filtration and do generous weekly water changes.

Feed flakes or pellets with frozen treats such as daphnia or bloodworms. Montezuma swordtails are mostly peaceful and a little shy, and they swim in the middle of the tank. Keep tank mates similarly sized, peaceful and happy in hard water, and avoid fin nippers and very small fish.

Females have no sword at all, so the sexes are easy to tell apart once the males mature. Males get competitive with each other, so keep just one male per group, or a larger group with several females. Either way, females should outnumber the males.

Females give birth to live, fully formed fry rather than laying eggs. Montezuma swordtails breed readily, and adults will eat the fry, so give dense planting or cover for survivors. Never release unwanted fish or fry into local waterways, and check your local rules before keeping or rehoming them.

Good to know

The Montezuma swordtail, Xiphophorus montezumae, is a livebearer in the family Poeciliidae. Its body runs about 6 to 7.5 cm, but a mature male's sword roughly doubles his total length.

In the wild

Montezuma swordtails come from the Rio Panuco basin in northeastern Mexico, across San Luis Potosi, Tamaulipas and Veracruz. They live in hard, alkaline springs and flowing streams with cooler, well-moving water.

Common questions

Related species

• 

  Northern mountain swordtail

  Xiphophorus nezahualcoyotl

  3.5 in (9 cm) · 29 gal (110 L)

  3.5 in (9 cm)29 gal (110 L)68–79°F (20–26°C)

• 

  Green swordtail

  Xiphophorus hellerii

  5.9 in (15 cm) · 20 gal (76 L)

  5.9 in (15 cm)20 gal (76 L)68–82°F (20–28°C)

• 

  Sheepshead swordtail

  Xiphophorus birchmanni

  2.8 in (7 cm) · 24 gal (90 L)

  2.8 in (7 cm)24 gal (90 L)68–81°F (20–27°C)

• 

  Kallman's swordtail

  Xiphophorus kallmani

  4.1 in (10.5 cm) · 29 gal (110 L)

  4.1 in (10.5 cm)29 gal (110 L)73–82°F (23–28°C)

• 

  Pygmy swordtail

  Xiphophorus pygmaeus

  1.6 in (4 cm) · 11 gal (40 L)

  1.6 in (4 cm)11 gal (40 L)75–82°F (24–28°C)

• 

  Southern platy

  Xiphophorus maculatus

  2.8 in (7 cm) · 10 gal (38 L)

  2.8 in (7 cm)10 gal (38 L)68–79°F (20–26°C)