Livebearer species have dominated the top of the list of popular aquarium fish for as long as any aquarist can remember, especially for beginning aquarists. They’re easy to keep and breed, colorful, and will cheer up any tank with their lively behavior.
One of our favorite livebearer species is the swordtail (Xiphophorus hellerii), which set themselves apart from the rest with their ornate tails. Below, find everything you need to know to ensure your swordtails thrive and even breed in your tank!
| Name (common, scientific) | Swordtail, Xiphophorus hellerii* |
| Minimum tank size | 30 gallons (long) |
| Minimum group size | 3 |
| Temperature | 68-82 °F |
| pH | 7-8 |
| Difficulty level | Easy |
Swordtail appearance & natural habitat
Appearance
Swordtails belong to the family Poeciliidae, the tooth carps. This makes them closely related to guppies, mollies, and platies—all highly popular aquarium fish collectively referred to as “livebearers”. They’re known for their ability to give birth to live young rather than laying eggs like most other species.
This species sports the typical tooth carp look, with an upturned mouth to catch bugs, a streamlined body, bright colors, and fan-shaped tail. Their swimming style is wiggly and they’re always on the move. Females may have very round bellies, indicating they’re gravid (pregnant).
True to their name, male swordtails sport extra-long fin rays on the bottom of their caudal fin (tail): the “sword”. They also tend to be more brightly colored than the females.
Did you know? X. hellerii, today’s subject, isn’t the only member of its genus to be kept as an aquarium fish. The ultra-common platy fish (X. maculatus) can be found at every pet store. There’s also a beautifully speckled species that sports an ultra-long sword: the Montezuma swordtail, X. montezumae.
Swordtail colors
Wild-type swordtails are actually very nice to look at, with olive green base coloration and a bright red stripe running horizontally across the body. The males’ swords are yellowish with black edges.
It doesn’t stop here, though! Selective breeding has produced a dazzling range of color varieties, with some fishkeepers dedicating entire fish rooms to producing the most beautiful swordtails possible.
Some of the swordtail color morphs you may come across at your local fish store include:
Tap to view the swordtail color list
- Albino swordtail: not a true albino, but lacks melanin and has red pupils. Can occur in combination with many of the below.
- Koi, Santa Claus, or kohaku swordtail: orange and white, sometimes comes in albino form or with black tail.
- Showa or sanko swordtail: a kohaku swordtail with black speckling on the body.
- Pineapple swordtail: yellowish on the face with a gradient to bright orange on the tail fin.
- Red swordtail: does indeed look very reddish, rather than the normal orange tone.
- Neon swordtail: similar to wild color, often with some extra orange.
- Black swordtail: may have silver speckling and lighter fins.
- Red wag swordtail: reddish-orange with a black tail.
- Marigold swordtail: with a color gradient from gold (face) to orange (tail).
- Vampire swordtail: similar to red swordtails, with long fins and red eyes.
- Berlin swordtail: reddish-orange with black speckles.
- Tuxedo swordtail: various body base colors with black coloration running from halfway down the body to the tail.
- Pink comet swordtail: pale body base color with orange extremities and black tail edges.
- White swordtail: entirely silvery-white in color.
- Alpha swordtail: entirely black with differently colored fins (often orange).
- Micky Mouse swordtail: one large and two small dots at the base of the tail, which look a little like a Mickey Mouse face.
The list above is not complete, but you probably catch our drift: there’s lots to choose from. And when your swordtails breed (more at the bottom of this guide), new and fun color variations may pop up in the fry!
There are also a few different body fin shapes out there, such as:
- High fin swordtail: with a lengthened dorsal fin.
- Balloon swordtail: bred for a very deep, round body; usually with a high dorsal fin.
- Double swordtail: also has a sword on the top end of the tail fin. Don’t confuse it with the double swordtail (or lyretail) guppy!
Did you know? Certain swordtail colors come from crossbreeding them with platy fish. These belong to the same genus, but naturally sport a wider range of colors and patterns. Examples include blue, metallic, and speckled. In fact, most swordtails nowadays aren’t “pure”, but swordtail-platy mixes.
Natural habitat
Swordtails are naturally found in Mesoamerica: Mexico, Guatemala, Belize, and Honduras. Here, like similar tooth carp species, this species has the unique ability to inhabit both fresh and brackish (salt, but below marine level) waters. It isn’t picky about habitat at all, although it does prefer shallower waters up to around 5ft in depth.
These livebearers can be found in freshwater lakes, ponds, streams, rivers, lagoons, and more. The water can have a rocky to muddy substrate and can be clear or very murky, while flow levels range from zero to quite strong. There’s usually not much in the way of plants present.
The IUCN Red List considers Xiphophorus hellerii to be a species of Least Concern, meaning it’s not threatened in the wild. The organization notes that although parts of its natural habitat are under pressure due to human activity, it’s highly adaptable and can sometimes survive in badly polluted waters.
Did you know? Because they’re hardy and adaptable, swordtails have a strong invasive potential. And indeed, escaped aquarium fish have already established themselves in countries as varied as Australia, Morocco, Turkey, Brazil, and many more. This can be problematic for the local ecosystems.
Swordtail aquarium
If you’re interested in setting up your own swordtail aquarium or introducing swordtails in your community tank, make sure your set-up is at least 30 gallons (long). This is an active species that needs to be kept in groups, and don’t underestimate their adult size! They’ll make maximum use of this space.
Although it’s not something they’d generally find in the wild, cover in the form of tall and/or floating plants will be appreciated by your swordtails. As always, the tank should be filtered and fully cycled.
Water Quality
Unlike many other popular aquarium fish, which like their water soft and acidic, swordtails should ideally be kept in relatively hard and basic water. That being said, as should be clear from the section on natural habitat, this species really isn’t that fussy.
Try to aim for a pH between 7-8 and a TDS between 100-450ppm. The same goes for temperature: anything between 68-82 °F should be fine. In fact, many aquarists report their swordtails having no issues with even lower temps.
Tankmates
When figuring out with fish will be compatible with your swordtails, keep in mind these livebearers’ preferred water parameters as well as their temperament. Go for species that don’t mind harder water and a pH above neutral. Any timid fish that might be stressed out by the swordtails’ very active behavior are best avoided.
Other livebearers, like guppies and mollies, work well as swordtail tankmates. Platies are also a good option, though avoid them if you don’t want the two species to interbreed.
You can also try:
- Catfish that don’t mind a higher pH, like the hardy bristlenose Pleco
- Schooling fish like rosy barbs
- Rainbowfish like Boesemani
- Danios like the zebra danio
- Tetras that don’t mind a higher pH, like the emperor tetra
- Rasboras that don’t mind a higher pH, like the harlequin rasbora
Swordtail diet
Like many other aquarium fish, swordtails are omnivores. They will take a bite out of nearly everything that enters their tank and is even remotely edible! In the wild, they’ve been found to eat plants, bugs, worms, detritus, algae, insects that have fallen into the water, and more.
To keep your swords happy and healthy in captivity, use a high-quality omnivore food as a staple. Something that mentions “color enhancing” and contains carotenoids like astaxanthin can help bring out the red tones in orange or red fish.
As variety is the spice of life, supplement their diet with a variety of options. (Thawed) frozen foods, algae tabs, blanched veggies, and even (home-bred) live foods will all be much appreciated.
Breeding swordtails
For many aquarists, breeding is what it’s all about when keeping swordtails. Like other livebearer species, this fish is extremely prolific, with females being almost constantly gravid.
A great breeding project for beginners, though you’ll have to make sure you’ve got a home lined up for excess fry! Some fishkeepers actually like to keep their swordtails with a carnivorous tankmate like golden wonder killifish (Aplocheilus lineatus) for the purpose of population control. These predators will consume small fry, but leave the parent fish alone.
To breed your swordtails, all you have to do is combine well-fed males and females and make sure the water quality is high. The fish will take care of the rest. Because swordtails do tend to eat their own young, it’s a good idea to plant the aquarium heavily. This gives the fry a chance to hide during the vulnerable first few days. It also allows them to feed on nutritious biofilm and infusoria that collects on leaves.
Want to go the professional route and breed your swordtails for certain traits (such as color) while ensuring maximum chance of survival? Your best bet is to set up a second tank to raise the fry in. This guarantees higher survival rates and allows you to select the best specimens to further refine the line you’re working on.
The perfect swordtail aquarium?
Looking to get into keeping swordtails and want to make sure everything gets set up right so you’re off to a good start? FantaSEA aquariums can set up and stock your new swordtail aquarium for you. We can even come back regularly to maintain it, so all you have to do is enjoy your new tank!
You can contact us for more information or a quote.
