Swordtail Fish


Family: Poeciliidae Swortail FishXiphophorous hellerii
Latest Reader Comment - See More
Swordtails do not change sex, the situation you are referencing is a late developing male which occurs when there is already large male in the tank. Other males... (more)  Trevor

   The most popular fish next to the Guppy is most certainly the Swordtail!

   The Swordtail is similar in shape to both the Platy and the Guppy though it has a bulkier body and a "sword" extending from the bottom of the male's tail fin. Today it is often thought to be named for this "sword" shaped extension of its tail fin, but the Swordtail was actually named for the sword like appearance of the male's anal fin!

   A beautiful male sporting a "sword" tail is one of the most striking physical characteristic possible by any aquarium fish. Even though there is no apparent purpose for this tail, it is 1/4 to 1/3 the total length of the fish. The wild species have an even more majestic tail, with swords up to 6 inches (15 cm). Though the "sword" tail is shorter in tank bred specimens it is complimented by the wonderful colors that are now available.

   Like the platys, swordtails have been interbred to produce all kinds of interesting colors and different types of finnage. Some of the more common Swordtails are: Red, Red Wag, Red Tux, Painted, Neon Green, Marigold (and wag), Pineapple, Black, Red Twin bar, Sunset, and Gold Tuxedo swordtails.

   Extremely popular because they are one of the prettiest fish, the Swordtails are also easy to breed, fast growing and readily available.They are generally peaceful lively fish that swim in loosely grouped schools. Even though they are considered a good community fish, there are potentially many different behavior patterns and temperments. The individual fish vary from peaceful harmonious tankmates to bullies. Older males especially can tend to be aggressive toward each other and other species.

   Swordtails do best in a well planted tank with lots of room to swim around. Provide floating plants to protect the young as the parents often eat their fry. Like all livebearers, they do like a bit of salt though it is not necessary.


What's in the name?
Xiphophorous means "bearing a sword"
hellerii named for Carl Heller


For more Information on keeping this fish see:
Guide to a Happy, Healthy Freshwater Aquarium

Geographic Distribution
Xiphophorous hellerii
Data provided by FishBase.org
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Cyprinodontiformes
  • Family: Poeciliidae
  • Genus: Xiphophorous
  • Species: hellerii
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Swordtail Fish - Quick Aquarium Care
  • Size of fish - inches: 4.5 inches (11.43 cm)
  • Minimum Tank Size: 15 gal (57 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Very Hardy
  • Temperature: 68.0 to 82.0° F (20.0 to 27.8° C)
  • Aquarist Experience Level: Beginner
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Habitat: Distribution / Background

   The Swordtails are found in Central America from the Atlantic slopes of southern Mexico to Guatamala.
   There are several color varieties of the Swordtail Xiphophorous helleri as well as a variety of other Swordtails species. The original Swordtail Xiphophorous helleri the most available and the other species, though similar, are not always as large and are often more delicate.
   The Spotted Swordtail was introduced as early as 1864, while the popular Green Swordtail was first introduced in 1909.

  • Scientific Name: Xiphophorous hellerii
  • Social Grouping: Groups - Enjoys being with other swordtails even though it is not a schooling fish.
  • IUCN Red List: NE - Not Evaluated or not listed


   Swordtails come in many colors and mixtures of colors, even in wild strains, that including red, green, black and albino though the most well known is red. There are now lyretail and high-fin varieties as males have been developed with exaggerated finnage and with two swords instead of one. Even some females also now have a sword. Most crosses are between the Platy or Moonfish Xiphophorous maculatus and the Swordtail Xiphophorous helleri.

Picture of a Pineapple Swordtail, Female Pineapple Swordtail (female) Xiphophorous hellerii

Popular cross bred Swordtails:
   The Green Swordtail has a green body with red and yellow along the lateral line of the sides. The Green Wagtail Swordtail is this fish crossed with a Wagtail Platy and the Green Tuxedo Wagtail Swordtail is this fish crossed with a Tuxedo Wagtail Platy.
   The Red Swordtail is a Cross between the Green Swordtail and the Red Platy, sporting different shades of red and called the Brick-red Swordtail and the Velvet Red Swordtail. There is also the Red Wagtail Swordtail and the Red Tuxedo Wagtail Swordtail.
   A Variegated Swordtail is a mixture of colors with no set pattern.
   The Hybrid Swordtail, is the same fish as the Salt-and-Pepper Platy. No two fish are alike but contain bits of black, red, yellow, and green blotches. If they retain the "sword" then they are called a Hybrid Swordtail rather than Salt-and-Pepper Platy.

  • Size of fish - inches: 4.5 inches (11.43 cm) - The females get up to 4.5 inches (12 cm), males are somewhat smaller at 4.0 inches (10 cm).

Fish Keeping Difficulty

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

   Since they are omnivorous the Swordtail will generally eat all kinds of live, fresh, and flake foods. To keep a good balance give them a high quality flake food everyday. Feed brine shrimp (either live or frozen) or blood worms as a treat.

  • Diet Type: Omnivore - This fish is an ominvore, however it appreciates a higher vegetable component in its diet. Supplementing processed foods with blanched lettuce is an excellent way to facilitate this need.
  • Flake Food: Yes
  • Tablet Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day

Aquarium Care

  • Water Changes: Monthly

Aquarium Setup

  • Minimum Tank Size: 15 gal (57 L) - Fifteen gallons could house a single individual with some company although this fish would be much happier in at least a 20 gallon tank with a few of its own kind. Generally it is best to keep a single male with a small harem of females unless the tank is large enough to house a more evenly mixed group.
  • Substrate Type: Any
  • Lighting Needs: Moderate - normal lighting
  • Temperature: 68.0 to 82.0° F (20.0 to 27.8° C)
  • Range ph: 7.0-8.3
  • Hardness Range: 12 - 30 dGH
  • Brackish: No - This is not a brackish fish, however it does seem to appreciate this addition of a little salt in the water. Around 1-1.25 teaspons of aquarium salt should suffice. Removed water should be replaced with salted water, however if the aquarist is topping off due to evaporation freshwater should be used.
  • Water Movement: Moderate
  • Water Region: Middle

Social Behaviors

   They are generally considered a good community fish although they will sometimes eat their own (and other fishes) fry. Occasionally a Swordtail can become a bully, especially older males.

  • Temperament: Peaceful - The males develop a distinct hierarchy. This fish, particuarly of the male gender, may become more bellicose with age. This fish can have quite extensive fins which are often too tempting for fin nippers to resist so avoid combining these fish with them altogether.
  • Compatible with:
    • Same species - conspecifics: Yes
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Threat
    • Shrimps, Crabs, Snails: Safe - not aggressive

Sex: Sexual differences

Only the male has the "sword" extension on the bottom of the tail fin. The male is also slimmer and has a "sword" shaped anal fin called a gonopodium. The female has a fan shaped anal fin, is rounder of body, and will have a spawning patch at breeding time. 

There is an occasional tendency for a male to be slow to develop a "sword" on his tail, especially if a large dominant male is present. When a dominant male becomes old or affected by parasites then this slow developing male may emerge. On occasion if there is no other male, the female may even attempt courtship with another female, though they are infertile.

Breeding / Reproduction

   The female Swordtail will generally have between 20 - 100 fry, usually up to 80. See the description of how to breed swordtails in Breeding Freshwater Fish - Livebearers.

  • Ease of Breeding: Easy


   The Swordtail is readily available.


Animal-World References

Author: David Brough, CFS & Clarice Brough, CFS.
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Lastest Animal Stories on Swordtail Fish

Trevor - 2014-09-15
Swordtails do not change sex, the situation you are referencing is a late developing male which occurs when there is already large male in the tank. Other males will develop slower until they reach a size that can compete with the tanks dominant male and will then develop their male characteristics. I have researched it and seen t twice in my own tanks, after which the late developing male would go on to father many fry of his own. This I am sure of from pairing the new males with young virgin females to be sure the changing of sex did not occur.

  • Clarice Brough - 2014-09-15
    You're absolutely correct Trevor. Thanks so much for bringing this to our attention, we will adjust the information right away.
Paige Felbaum - 2004-04-06
I think this is a very wonderful fish. They come in all different colors and will breed easily. But if you are like me and breed your fish these are a good fish to start on. The fry are kind of hard to take care of but if you know how to do it they will probably live. They are very easy to take care of and live a while. My oldest one is almost 7 months now in a heated aquarium around 75 F and fed twice a day. He lives with a mollie, african dwarf frog, female guppy, tiger barb, red platy and 5 jumbo neon tetras.(in a 10 gallon tank)

  • Debbie - 2010-03-16
    My female swordtails tail had a white spot on it she was pregnant, after she had the babies it went away and she is doing fine I use bottled spring water.. but I have a hard time having the babies live... they die on me. I have them in a separate little tank and feed them the flake food... how do I take care of the babies and keep them living so I can breed them?
  • Caitlin Perello - 2010-06-02
    I think you might want to get a bigger tank for all of those, especially with a frog in there. In my ten-gallon tank, I have a pair of swordtails (the female I believe to be pregnant), and my marble angelfish.
Josh - 2009-01-29
Hey everyone. This is one of the best websites for pets. I use this one and 2 others. These the only 3 I use. First off thanks to this website, I have become a big help for my neighbor who I gave fish to. If you are trying to find a way to feed your swordtails (and possibly snails and/or pleco) without taking a lot of money out of your wallet, you should try feeding them blanched zucchini (I think that is how u spell it). Blanched means that you cut it into slices, put it in a pot of boiling water for about a minute, and then put it in a pot of ice cold water. It brings out the color and makes it sink. All you do is drop it in, either with the skin (for if you have plecos and snails in the tank or if you want to give more nutrients), or without the skin (easier for swordtails to eat).

Sarah . A . - 2004-01-18
I like going to this site for answers to my livebearer questions.I own 4 swordtails,if you include the baby fry,1 large female guppie,and 30 of her fry.People say livebearers are only for beginners,but I like having fish that are easy to breed and tell apart.I could not imagine having a tank without atleast 2 livebearers.I would like to see more pictures or swordtail colors on this site.I enjoy seeing some of the vast color types!Thanks!

imah - 2014-09-07
Hello I have a leopard pleco and I think it is pregnant so I have been doing some research. I needed to see if it was an egg layer or a live bearing fish. I searched it up and one site said that it was a live bearing fish and another site said that it was an egg layer. Also if it is a live bearing fish what are some signs to look for when it is about to give birth? I hope someone can help. Thank you.

  • Clarice Brough - 2014-09-07
    Catfish are egglayers, as are the majority of freshwater fish species. Livebearers are mostly swordtails (like this fish), guppies, mollies,  and a few others. You can see an overview of livebearing fish on the main page of this Livebearer Aquarium Fish Atlas.

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