How big does Swordtail get?

Swordtail reaches an adult standard length of 6–12 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.

What water does Swordtail need?

22–28 °C, pH 7–8.3, 10–20 dGH, 4–12 dKH. At 6 °C wide it is one of the more forgiving ranges.

What is the smallest tank for Swordtail?

At least 90 L, and no shorter than 80 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is a schooling fish: keep at least 3 together. Fewer than that and it hides, loses colour, and aggression has nowhere to spread.

What is Swordtail like to keep?

Temperament: peaceful. Difficulty: beginner. It occupies the middle and is omnivore. With plants it is "Nips new growth".

Can Swordtail be kept with its most common tank mate?

The checker returns "Can be kept together". Swordtail and Guppy is a well-established pairing. Individual fish still differ; the record says "usually fine", not "guaranteed".

G-01 / 04Freshwater

Swordtail剑尾鱼

Xiphophorus hellerii · Poeciliidae

A 12 cm livebearer whose males trail a long sword, and one of the easiest hard-water fish.

Illustration to come

G-01 / 04 · Swordtail Xiphophorus hellerii

SpecificationsFish atlas

Name: 剑尾鱼
Scientific name: Xiphophorus hellerii
Family: Poeciliidae
Origin: Central America (southern Mexico to Honduras)
Adult size: 6–12 cm
Temperament: Peaceful
Diet: Omnivore
Water level: Middle
Level: Beginner
School size: ≥ 3
Min. tank: 90 L
Min. length: 80 cm
Plant safe: Nips new growth

Water requirementsFreshwater

Temp.22–28 °C

pH7–8.3

Hardness10–20 dGH

Alkalinity4–12 dKH

Units: temperature in °C, hardness in German degrees (dGH / dKH), marine salinity as specific gravity at 25 °C, volume in litres. These are the values recorded for the species and do not follow the site unit switcher.

Keeping notes

1The male sword grows after 6-8 cm and the fish jumps when startled, so a snug lid is required.
2Males chase each other nonstop; keep two or more females per male to spread the pressure.
3Likes hard, alkaline water and handles high-pH tap water better than most small fish.
4Omnivorous with a plant lean on flakes, spirulina and some live food; 12 cm adults need an 80 cm tank.

Check a tank mate

Jump straight to the verdict for Swordtail against this one — no need to pick it again.

Frequently asked questions

How big does Swordtail get?: Swordtail reaches an adult standard length of 6–12 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.
What water does Swordtail need?: 22–28 °C, pH 7–8.3, 10–20 dGH, 4–12 dKH. At 6 °C wide it is one of the more forgiving ranges.
What is the smallest tank for Swordtail?: At least 90 L, and no shorter than 80 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is a schooling fish: keep at least 3 together. Fewer than that and it hides, loses colour, and aggression has nowhere to spread.
What is Swordtail like to keep?: Temperament: peaceful. Difficulty: beginner. It occupies the middle and is omnivore. With plants it is "Nips new growth".
Can Swordtail be kept with its most common tank mate?: The checker returns "Can be kept together". Swordtail and Guppy is a well-established pairing. Individual fish still differ; the record says "usually fine", not "guaranteed".