Northern mountain swordtail

Care at a glance

Overview

The northern mountain swordtail is an active swordtail for a cool tank with strong flow. It is easy to keep.

Caring for the northern mountain swordtail

Keep northern mountain swordtails in a group in a tank of at least 29 gal (110 L). Give them dense planting along the back and sides, with open mid-water swimming space and some hiding spots. They are active swimmers that work the middle of the tank.

They are subtropical fish, not warm tropical ones, so keep the water on the cooler side, at 68 to 79°F (20 to 26°C). Keep it neutral to slightly alkaline and moderately hard, at a pH of 7.0 to 8.0, with no brackish or blackwater needs. Run an oversized or over-rated filter to push strong flow through the tank and keep the water well oxygenated.

Feed a varied diet of flakes or pellets with frozen and live foods and some vegetable matter. Northern mountain swordtails are mostly peaceful but boisterous. Pair them with similarly robust species, and avoid slow, long-finned fish that can get nipped.

Males chase and harass females persistently, so keep a skewed sex ratio of one male to two or more females. Males carry a sword, an extension of the lower fin rays of the tail.

Northern mountain swordtails are livebearers, giving birth to fully formed fry rather than scattering eggs. They are easy to breed, but adults readily eat their own fry. Use dense plants, spawning mops or a separate trap to save the young. Never release them into local waterways, where they are non-native, and check your local rules before keeping or moving them.

Good to know

The northern mountain swordtail, Xiphophorus nezahualcoyotl, is a livebearer in the family Poeciliidae. It is named after Nezahualcoyotl, the poet-king of pre-Columbian Texcoco in central Mexico. Counting the male's sword, total length runs to about 3.5 in (9 cm), while females reach roughly 6 cm in body length. It is uncommon in the hobby and mostly kept by livebearer specialists.

In the wild

Northern mountain swordtails come from fast, cool montane creeks in the Rio Tamesi and Panuco drainage of San Luis Potosi, Mexico. They live at elevations up to around 1200 m.

Common questions

Related species

• 

  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)

• 

  Montezuma swordtail

  Xiphophorus montezumae

  5.5 in (14 cm) · 32 gal (120 L)

  5.5 in (14 cm)32 gal (120 L)68–79°F (20–26°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)

• 

  Variable platy

  Xiphophorus variatus

  2.8 in (7 cm) · 15 gal (55 L)

  2.8 in (7 cm)15 gal (55 L)68–79°F (20–26°C)