TankBud

Variety of Green swordtail

Red swordtail

Xiphophorus hellerii

One of 6 varieties of Xiphophorus hellerii · See all varieties →

FreshwaterFish

Red swordtail (Xiphophorus hellerii)
The Wet Spot Tropical Fish · Used with permission

Varieties · Xiphophorus hellerii

See all 6 →

Care at a glance

Temperature
68–82°F
20–28°C
pH
7.0–8.0
Adult size
5.9 in
15 cm
Minimum tank
20 gal
76 L
Temperament
Peaceful
Social behavior
Social
Swim level
Middle
Difficulty
Beginner
Breeding
Livebearer · Easy
Rarity
Very common
Family
Poeciliidae

Overview

The red swordtail is the default shop swordtail, sold plain red or as a wagtail with black fins. Color quality varies between farms, from an even deep red to patchy orange with dark flecking. It is a peaceful community fish that a beginner can keep with ease.

Did you know

A red swordtail male's sword is shorter than a wild green male's, a side effect of the platy blood in the line. Platies have no sword at all, and the crossing that brought in the red also trimmed it.

Caring for the red swordtail

Red swordtails do best in a small group, in 20 gal (76 L) or larger. They are active, cruise the middle of the tank and like some length to swim. Give them plants along the edges, open space down the middle and a moderate flow.

Hard, alkaline water at 68 to 82°F (20 to 28°C) and a pH of 7.0 to 8.0 keeps them comfortable. They eat a quality flake or pellet with some vegetable matter, plus the odd frozen treat.

Red swordtails are peaceful and safe in a community tank. More females than males spreads out the males' attention. Pick individuals if the shop will let you, since a tank of red swordtails is rarely uniform.

Males show a sword and a narrow, rod-shaped anal fin, so adults are easy to sex. Females are larger bodied and lack the sword. Red swordtails give birth to live young rather than laying eggs. A female can store sperm and produce several broods from one mating, so expect fry and give them plants to hide in.

Good to know

The red swordtail's color sits in erythrophores, the red pigment cells. Domestic red lines stack far more of them than a wild green fish carries. The color breeds mostly true, though off-colored culls turn up in most spawns. The wagtail black on the fins also came out of platy crosses. Hobby genetics accounts put two of the three alleles behind it in Xiphophorus maculatus.

In the wild

The red swordtail is a farm color, not a wild one. The USGS nonindigenous species database lists it as a hybrid of Xiphophorus hellerii and the platy Xiphophorus maculatus. The database notes that the two are often crossbred in captivity. Hobby accounts trace the red back to red platy stock, and farms have worked that cross for roughly a century. No fish this color swims in the wild streams the species comes from.

Weekly picks

Tank mates

The red swordtail is a peaceful, social species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

Is a red swordtail a different species from the green swordtail?

No. A red swordtail is a variety of the green swordtail, Xiphophorus hellerii, and it wants the same tank, water and food as the species.

What size tank does a red swordtail need?

A red swordtail needs at least 20 gal (76 L). It spends most of its time in the middle.

What does a red swordtail eat?

A red swordtail takes a quality flake or pellet with some vegetable matter. Give it the odd frozen treat too.

How big does a red swordtail get?

An adult red swordtail reaches about 5.9 in (15 cm).

How can you tell a male red swordtail from a female?

Males show a sword and a narrow, rod-shaped anal fin, so adults are easy to sex. Females are larger bodied and lack the sword.

How does a red swordtail breed?

Red swordtails give birth to live young, and a female can store sperm for several broods from one mating. Expect fry, and give them plants to hide in.

Related species