The swordtail fish is originally from Central and North America but it can now be found on every continent. It can adapt and thrive in a variety of conditions.

The scientific name is Xiphophorus hellerii.

In the wild they prefer fast moving waters such as rivers and streams though they will also survive in slower moving water such as ponds and canals. This differentiates them from their fellow Xiphophorus the Platy that prefers calmer water.


The Natural habitat of the green swortail stretches from Mexico to Honduras.

Xiphophorus hellerii. Placeholder
Xiphophorus hellerii.


Swordtails come in a variety of colors including a bright orange, green, and even neon.

They are one of the largest live bearing fish. The male can grow to five or six inches. Females tend to be slightly larger than males but do not grow the swordtail. The females have rounder bodies.

It is easy to differentiate the male from the female due to the sword that grows from the tail fin of the male. Thus, the name swordtail. The sword tail doesn’t grow until the male is an adult, usually around eight months.

The male also develops a gonopodium which is a sexual organ.

The sword of a male fish in the wild can grow much larger than fish kept in tanks.

Reproduction and Life Span

The decision of who to breed with seems to rest with the female and she appears to prefer males with a longer sword when given the option between two males.

They breed quickly and a female will give birth approximately every twenty-eight days. An average of thirty fry are born each time and sometimes as many as eighty.

The life span of a swordtail is longer than many live bearers. Life span is longer for a swordtail that is well cared for in a tank than in the wild. It’s not unusual for them to live up to five years with the average being three years.

The swordtail is closely related to the Platy and they can interbreed.

Diet in the Wild

Swordtails are omnivores and will eat a wide variety of foods including plant foods with Spriulina. They also eat mosquito larva and worms.

Keeping Swordtail fish in a Tank

Due to its hardy nature the swordtail is a popular fish for fresh water tanks. They come in a variety of colors that can make your tank visually appealing.

Preparing Your Tank

Because of the large size of the swordtail a standard ten gallon tank is not a good option. A 30 gallon tank or larger is recommended to keep swordtail fish. Once your swordtails start breeding a larger or second tank may become necessary.

The tank needs to be carefully rinsed out, do not use chemical cleaners, before its used.

It’s best to fill the tank with distilled water if possible. If you use tap water you’ll need to use tablets you can purchase at a pet store to get the correct ph balance. 7 to 8 ph is optimal. Hardness should be 10 to 20 degrees DH.

Tap water contains too much chlorine for your tank so you’ll need to buy chlorine remover. This is available at a pet store that sells aquariums supplies.

You may need to purchase bacteria starter, as well. This is not always necessary if you add plants and set your tank up at least two weeks before adding fish.

A good filter is necessary and a heater. The temperature in the tank needs to be 72 to 82 degrees.

A half inch of gravel should be placed on the bottom of the tank. Use rocks for decorations and not wood which can affect the ph levels in your tank. Live plants, including some floating ones, are a good addition to the tank.

Your tank will need a secure lid because swordtails are notorious jumpers.

Never set your tank in direct sunlight.

It can take a while to get the ph level and temperature in your tank is correct so set it up well advance of adding your fish.

Caring for Swordtail Fish

Swordtails require minimal care but there are some things you must do to keep your fish healthy.

Adult swordtails only need to be fed once or twice a day. Juveniles need to eat two or three times and newborns six times a day. They will eat a diet of flakes, frozen food, black worms, mosquito larvae, and live food such as shrimp brine. They need some food that contains algae to remain healthy. With the correct lighting and plants this will grow in the tank.

It is important not to overfeed. Nothing should be left uneaten after two minutes. If there is, you’ll need to feed less the next time. Overfeeding will cause cloudy water.

Breeding Swordtail Fish

Swordtail fish are easy to breed and require little help from you. In fact, if you don’t wish your fish to breed you’ll need to fill your tank with all female fish. However, female fish can store sperm. So if they’ve previously been in a tank with males fish they may still give birth.

These fish give birth to live baby fish, called fry, as quickly as every 28 days. As many as eighty fry can be born at one time though thirty is average. It is best to isolate the fry or the adult fish will eat them. If you don’t want to isolate them at least have a lot of plants in your tank where they can hide.

However, because these fish are so prolific, your tank can quickly become overpopulated. This is why some owners don’t stress over separating the young.

Possible Problems

When you buy new fish, always keep them isolated for a few days to assure they are healthy.

Male swordtails can become aggressive if there are too many in one tank. It’s best to limit one male to every three females.

Most health problems come from a problem with water quality. Be sure and check your tank periodically to be sure ph levels are correct, there’s not too much ammonia, and that the temperature is correct. The tank will need to be cleaned on a regular basis.

If any of your fish show signs of fin rot or develop white spots remove the diseased fish and place in a separate holding tank. These symptoms can be caused by a bacterial infection which is often contagious.

By joining online forums you can visit with other swordtail aquarium enthusiast and share information on the proper care of your fish.

Swordtails make an interesting addition to any aquarium and will thrive with basic care.