Swordtail Fish – Habitat, Care, Feeding, Tank Size, Breeding

Xiphophorus helleri, better known as Swordtail, is a member of the family Poeciliidae in the order Cyrinodontiformes.  The fish is closely related to Platy or commonly referred to as the Southern Platyfish, and like its relative, it has been used extensively in genetic and medical research.

They are so related that they can crossbreed with one another, and they do so regularly in the wild. But how well do you know swordtail? Well, stay with us as we dig deeper on this unique fish.


This species is an elongated fish, growing to about 5 inches or 13 centimeters long. They have unique types of fins with the extended pointed region at the bottom of the caudal fin and comes in a wide variety of colors.The Swordtail species is sexually dimorphic.

The male species are characterized by the extended tail, and the female is often larger than the male. The different sexes do share the same color palette. They are also commonly referred to as Green Swordtail or Red swordtails.

The original Swordtail had green with a red stripe on each side. Nowadays, the Swordtails are bred to achieve many color varieties and, as a result, various types exist.


Swordfish is a very popular fish from the rivers and streams of Central America on the Atlantic side and are also found in both South and North America. Their natural habitat stretches from Honduras, Mexico to Vera Cruz.

Swordtail fish are average-size fish; they don’t require very much space in the aquarium. However, since they are very active, they would benefit from having enough space to swim around. For one adult swordtail fish, the minimum tank size should be at least 15-gallons. But if you intend to add other fish, prepare to house them in at least a 29-gallon aquarium.

In general, Swordtail prefers moderately alkaline, hard water. The water should be from 12–30 dGH and an ideal water pH anywhere between 7.0 and 8.4.


Swordtail fish are omnivores that feed on proteins such as worms, larvae, and many more. However, they can eat plant and animal matter too. You can also give them quality flake food or live foods such as brine shrimp, daphnia, fruit flies, or mosquito larvae.

In an aquarium, they will eat any normal fish food. Swordtail fish also eat plenty of vegetation and algae in their natural habitat. Therefore, don’t forget their demand for proper herbivorous food. Try and supply them with a perfect mix of vegetation and protein to satisfy their exact diet requirements.

Water & Tank Requirements

The temperature of the water within the aquarium should be 64 – 82 degrees Fahrenheit. Keep in mind that direct sunlight can alter the tank’s temperature, as well as placement of the tank (near a cold draft or by a heat source). Try and provide live plants for your swordtails.

A densely planted aquarium almost mimics their natural habitat, and don’t forget to provide a cover and shade for the fish. Fake plants will also work; however, they don’t provide the dual benefits of oxygenating the water and improving water quality that live plants offer.

When selecting a filter for Swordtail, go for the bigger once. If you can afford it, you should always try to over-filter your tank, and Swordtails will enjoy the current that an over-filtered tank brings with it. Go for the HOB (hang-on-back) filters; they are the best choice since they are efficient and economical.


Swordtail fish is a very social, active species and enjoy good company, especially when housed with other swordtails or similar passive species. Two males Swordtail may cause problems for each other. They do not have to stand up fights like the Siamese Fighting Fish, but unless distracted by enough, females may squabble a bit.

Swordtails are a community fish, and suitable companions include the other smaller peaceful fish such as Guppies, Zebra Danios, Head and Tail Light Tetras, Rummy Nose Tetras, Emperor Tetras, Lemon Tetras, and White Cloud Mountain Minnows. Keep the larger types of tetras in schools of five or more to prevent possible harassment.


Breeding can begin as early as three months of age. Therefore, it is strongly advised that swordtails be separated after determining sex. The gestation period of Swordtails is about 28 days. For breeding, put a ratio of three females to each male.

Experiments show that female Swordtails prefer larger males with a long sword. Immature males look like females. An early developing male will usually end up as a smaller fish than a late-developing male.

Before the sword develops, the sex can be seen by the developing gonopodium. This is a modification common to others in this group of fish.

The Anal fin under the middle of the fish becomes elongated and is used to transfer the packets of sperm, called spermatophores, to fertilize the female. The gonopodium is functionally similar to the penis of mammals but structurally different.

To determine if the female is pregnant, you may notice the bellies growing bigger. However, the sure sign that they are close to giving birth is when they begin isolating themselves from the males. They will also suddenly become hostile towards the male swordtails.

A female about to give birth will disappear in one corner and restrict her movement within that area.  These fish are livebearers and can give birth to as many as 30 young fish at one time.

To make the fish happy, you need a couple of tanks or a large enough tank that you can place a divider in is the absolute bare minimum with size varying from five to a ten-gallons.

If you’re breeding show quality fish, a larger tank will give the animal more breathing and swimming space resulting in a healthier fish. A larger tank also helps the breeder in finding and removing fish as necessary.

Also consider other requirements such as floating foliage, breed boxes, nets, and tubing. Swordtails thrive with a bit of salt in their watery abode. For every ten gallons of water, add a tablespoon of aquarium salt.

After the birth of the babies, the fry tank should have its water changed at approximately 30% ratio each week. Refreshing the water offers a better environment for fry to grow into healthy, beautiful fish.


When adding new fish to the aquarium, leave them in the plastic bag, and allow the bag to float in the aquarium for about 30 minutes. This is the best way for the fish to become acclimated to the water temperature.

If this procedure isn’t done, the fish will become stressed at the change in water temperature. Stressed fish can result in diseased fish. With proper care and feeding and only keeping other non-aggressive tropical fish in the aquarium, your Swordtails should thrive well.

Updated: March 5, 2020

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