Swordtail Fish are fascinating fish for freshwater aquariums.
The Swordtail is a popular type of livebearer that is loved for their colors and community friendliness.
They look very similar to the Platy Fish but are identified by their larger size and the male’s long, pointed lower caudal fin.
This interesting livebearer is easy to care for and can adapt to changing water conditions. Their tank requirements are very flexible and they can fit into aquariums of all sizes, from Nano tanks to diverse underwater biotopes.
Keep reading to learn all there is to know about Swordtail Fish…
Table of Contents
Swordtail Fish 101
The Swordtail Fish (Xiphophorus hellerii) belongs to the Poeciliidae family.
This family includes all freshwater and brackish livebearers, including Mollies, Guppies, and Endlers. They actually share the Xiphophorus genus with the Platy fish and some people consider the Swordtail to be a long-tailed Platy.
Swordtails are native to Central America where they live in brackish water streams and range from Mexico to Honduras.
Over 30 different color morphs exist and they are best known for their iconic sword tail. However, it is only the males that have this tail.
Common color forms like red, black, and yellow will cost about $4 to $7. The more spectacular colors will cost at least $15, and groups of high quality specimens can run over $100.
- Experience Required: None.
- Nicknames: Green Swordtail.
- Color Forms: Various.
- Size: 5-6 inches.
- Tank Size: Minimum 15+ gallon.
- Tank Temperature: 70°F to 82°F.
- Beginner friendly
- Pairs well with other livebearers
- Very easy to breed
- Docile and sociable with others
- Males will compete for dominance
- Interbreeding with Platys is possible
- May overcrowd the tank with offspring
The Swordtail is best known for their pointed lower caudal fin that looks like a sword.
Only the males have a sword fin as females have short fan-like fins.
They have a torpedo shaped body that is wide at the front and thin towards the tail.
Their head has a small hump where the dorsal fin is attached, sloping down to a sharply pointed snout.
They have 7 fins in total, including a dorsal and caudal fin, paired pectoral and pelvic fins, and a single anal fin. Thanks to selective breeding there are many possible fin types.
The typical Swordtail has a short triangular dorsal fin and a fan shaped caudal fin with an extended lower half. The other 5 fins are short and very thin.
- On a Hi-Fin variety the dorsal fin is tall and wide like the sail of a ship.
- With the Longfin variety, all 7 fins are long and trail behind the body.
- Lyretail Swordtails have a split caudal fin that is extended at both ends.
In the wild these fish come in various shades of green against a bronze or tan base. The green color is concentrated at the lateral line.
Although the sword distinguishes the males from the females, the females are also up to an inch larger than males.
Swordtail Fish size will vary between 5 and 6 inches.
You can find several different types of Swordtail Fish.
The dorsal fins, caudal fins, or body shape can be modified by crossbreeding and selecting for different traits. Many of these breeds are the result of hybridization with a fancy Platy breed.
Hi-Fin Swordtails are named for their tall, wide dorsal fins. They are similar to the Hi-Fin Molly, another specialty breed of livebearer. In some cases the dorsal fin grows so tall that it folds over, creating a veil effect. Because these Swordtails are heavier they are also slower. This makes them more vulnerable to fin nippers, especially if their fin trails behind them. Hi-Fins can come in any color or pattern and can be crossed with Lyretails or Longfins. They are a little difficult to breed so they will be more expensive than other varieties.
Lyretail Swordtails have a split caudal fin which ends in threadlike extensions on both ends. The Lyretail effect causes the male’s sword to curl towards the tip. Lyretails are possible on any species of livebearer, including Guppies, Mollies, and Platys. They are valued for their elegant appearance and graceful swimming. A Lyretail can come in any color or pattern. The tail shape does not slow their swimming or decrease their activity level.
Longfin Swordtails have 7 long fins that trail behind them like a train. Just like a Lyretail, the sword can curve or curl towards the tip. The Longfin variety may be crossed with a Hi-Fin or Lyretail.
Veiltail Swordtails have a wide caudal fin that looks like a long, flowing veil. Veiltails are not very common and are very difficult to breed. However they are among the most elegant looking breeds on the market.
These fish can come in over 30 different color morphs. Here are a few of the most popular:
- Green: These wild type fish come from wild-caught lineages and are a bronze and green color. You can find them in shades from grass green to blue-green, and the color is centered around the lateral line.
- Red: Red is an iconic base color for Swordtails, including Koi, Red Velvet, and Red Wag. A Red Velvet fish features a deep blood red color, while Red Wag pairs the red base color with black fins.
- Koi: Koi morphs are bred in colors that match the most popular varieties of the Koi. Kohaku, or red and white, is the most common, but Koi morphs can also come in red and black Sanke and Showa formations.
- Pineapple: Pineapple is one of the most eye-catching color combinations. They have a deep orange dorsal side and a bright yellow ventral side.
- Gold: Gold Swordtails are a golden yellow with sparkling iridescent scales. Their body can have black or white spots, and a white underside.
- Wag: Wag morphs have a solid colored body with black fins. Red, Pineapple, Gold, and Orange are common base colors for Wags.
- Twin Bar: Twin Bar Swordtails have parallel black lines at the base of the caudal fin on both ends. The black bar may extend to the male’s sword.
- Black: This is a solid black fish with iridescent scales near the lateral line.
Swordtail Fish Breeding
Just like other livebearing fish, Swordtails breed very easily.
Most of the time they do not need any help.
If you have a mixed gender group then you may notice a few tiny fry swimming around your tank.
Purposeful breeding however will help make sure that most of the offspring survive and it also lets you select for the most desirable colors and traits. Breeding fancy morphs can be fun and profitable.
To get them in breeding condition you will need to raise the water temperature to 77°F. Use an air stone to add extra oxygen to the water. Feed them 3 high protein meals a day and increase the amount of live prey in their diet. Brine shrimp and bloodworms are the healthiest foods for breeding fish.
Supplement their diet with commercial foods that contain color enhancers. The deeper the male’s colors are, the more likely he will be able to entice the female into breeding.
When the female is gravid, the male will rub his sword against her abdomen to fertilize the eggs. The female can store his sperm for up to a year so the couple will only need to mate once.
Pregnant females are visibly swollen with eggs.
It takes 25 days for the young to develop inside the mother’s body. Once they are born you can remove the mother and raise the fry in a nursery tank.
The fry will not have yolk sacs so they need immediate access to food. You can give them a mix of powdered fry food and larval brine shrimp 3 times per day. The juveniles will be ready to join the main tank after a month.
Swordtail Fish are among the best fish for community tanks.
In the wild they live alongside other livebearers, including Platys and Mollies. In your aquarium you can keep them with anything that is not too large or too aggressive.
Other livebearers make the best tank mates. In addition to Platys and Mollies, they can live with Guppies and Endlers. Outside of livebearers they will get along with just about any small to medium sized community fish. The colorful Rainbowfish makes a great tank mate.
They do not spend very much time at the bottom of the tank so peaceful bottom dwelling fish such as Loaches and Catfish are good tank mates.
Kuhli and Yoyo Loaches will work well if your tank has a softer water hardness. In a cool water setup you can even include the Dojo Loach. However, you must keep the water temperature below 75°F.
Cichlids are generally not safe in this community but a few of the more peaceful ones are considered safe. The Bolivian Ram, German Ram, and Orange Chromide should not create any problems.
Cherry Barbs are safe with both short finned and long finned Swordtail.
You do not want to include any shrimp or snails in this tank. You also want to avoid any large, territorial, or hyperactive fish species. This means no large Cichlids, large Catfish, or Clown Loaches. You also do not want to add Goldfish as they require different water conditions.
Keeping Swordtail Fish Together
Swordtails do not school or shoal but they are happy to live in groups.
To prevent any aggression you should make sure that there are at least 2 females to every male.
When there are too many males in the tank these otherwise peaceful fish turn into fighters. Males will compete for dominance, territory, and potential mates. Removing the females from the group does not reduce this behavior. The males will still attack each other.
So long as you keep 2 or 3 females for each male in your tank, then your fish should be on their best behavior.
Can Swordtail Fish And Bettas Live Together?
Bettas and Swordtail Fish should not be kept together.
There are two main reasons why:
- Bettas need very soft water at a hardness of less than 10 dGH. The Swordtail, on the other hand, prefers a hardness of 12 dGH and above. While Swordtails can survive in lower water hardnesses, they will not be very healthy in a hardness as low as the Betta needs.
- Bettas are extremely aggressive. If they target the Swordtail then they will attack until the Swordtail is dead.
Swordtail Fish Care Sheet
This is an extremely hardy and robust fish.
They are well adapted to disturbances and changes in their environment, including seasonal variation, climate change, and human activity.
You should change their water and clean the substrate every 2 weeks. Make sure their water parameters remain stable and keep ammonia and other waste products out of the water column.
An extremely common bacterial infection that Swordtails suffer with is Columnaris, or Cottonmouth.
It is so common in livebearing fish that it is often known as Livebearer’s Disease.
This highly contagious bacterial infection is fatal if left untreated and can quickly spread to every fish in the tank. Despite its name, this disease does not affect the mouth. It manifests as a white, bumpy ulcer between the dorsal fin and pectorals.
If left untreated the infection can spread to the gills.
Cottonmouth is treated by adding aquarium salts to the water, and can also be treated with antibiotics. It must be caught early for the treatment to be successful. This disease can be prevented by vacuuming and rinsing your substrate every time you clean the tank.
These fish will eat whatever is available.
In the wild their diet is primarily made up of insects, worms, and zooplankton. They will eat whatever small invertebrates they can find in the water including shrimp and snails. If any algae or plant material is around then they will munch on that as well.
They will eat more live prey in the spring and summer, and greenery in the fall and winter.
To bring out their bright colors you should give them a diet made up of 50% protein, followed by healthy fats, fiber, and vitamins.
You can start by giving them protein packed flakes or pellets.
In addition to commercial foods you can feed them water fleas, brine shrimp, and bloodworms.
Supplement their diet with algae wafers and spirulina tablets to make sure they get enough fiber and greenery. The algae that grows in your tank will not be enough for them.
Swordtails must be fed 3 times every day. If you have difficulty keeping up with a feeding schedule then you may want to consider an automatic fish feeder.
Each individual in the group must be fed just enough to finish in under 3 minutes.
Any leftovers should be disposed of right away.
What Food Can They Eat?
These little fish have quite large appetites. Here is a list of the best things to feed your Swordtails:
- Fish flakes
- Fish pellets
- Water fleas
- Brine shrimp
- Algae wafers
- Frozen shrimp
- Frozen worms
The Swordtail is a peaceful and curious little fish.
They have an appetite for adventure and are happy to explore every level of the tank.
You will usually find them at the middle levels or in the backdrop of a planted tank. They will venture up to the surface from time to time.
Most breeds are active and swim very fast.
Others, like the Longfin, swim more slowly because of their unusual body shape.
They are not particularly timid or shy, unless there are large or hyperactive species in the area. They are otherwise very social with their tank mates and will get along well with other livebearers.
Habitat and Aquarium Set Up
Swordtail Fish are highly adaptable fish that are found in brackish and freshwater habitats all over the world. They will even thrive in manmade bodies of water, such as drainage basins and irrigation ditches.
Their natural habitat is fast-moving brackish water streams and rivers attached to coastal inlets. These areas usually have a water hardness over 12 dGH.
While they prefer areas with temperatures over 72°F they can adapt to both low and high water temperatures. They are often found in temperate water areas outside of their natural range.
Most importantly, their habitat must be densely packed with underwater plants.
Floating and rooted plants are used as shelter, cover, and breeding grounds.
To replicate these conditions inside your aquarium you will need the following water parameters:
- Temperature: 70-82°F (74-77°F is ideal)
- pH: 7.0-8.0
- Water Hardness: at least 12 dGH
It is not uncommon to catch them trying to jump up out of the tank so a hood is an absolute must.
Your filter should be able to generate some moderate to high flow but it does not matter what kind of filter you use. The light intensity will depend on what is required by your plants. You will need at least 3 watts of light per gallon for 8 to 12 hours a day.
This fish is not very picky about substrate as it spends most of its time at the middle levels of the tank. We recommend dark colored sand or mud, enriched with fertilizer for growing plants.
These fish do not care much for decorations outside of plants.
Plants are the most important part of a Swordtail tank. You should choose low growing foreground and midground species that allow for open space at the middle levels.
|Minimum Tank Size
|Moderate to High
|Dark sand or mud
What Size Aquarium Do They Need?
If you are starting off with just one or two Swordtails then you will need at least a 15 gallon tank.
You should add 5 to 10 gallons for each additional Swordtail.
Keep in mind that some fancy breeds will need a larger tank. Use at least a 25 gallon tank for a Hi-Fin or a Longfin, and at least 30 gallons for a Veiltail.
History and First Sighting
Swordtails were first discovered by Johann Jacob Heckel in 1848.
Their ability to give live birth astounded the scientists of the period!
In the early 20th century these fish were moved into the laboratory and used to study genetic traits. In 1930 Texas State University established the Xiphophorus Genetic Stock Center for the purpose of examining this fish’s important link to genetics in the field of medicine.
These fish were used purely for medical research until the 1960s when they entered the aquarium trade.
However, it was not until 1980 when the first ornamental color morphs began to appear.
As their popularity increased so did the number of color morphs. There are now more than 30 different color morphs.
By the 1990s this species had been introduced to over 31 different countries. Now, this species has established populations all over the world and it continues to be a popular livebearing fish in both the aquarium trade and the aquaculture field.
Should You Keep The Swordtail Fish? (Summary)
|Other Common Names:
|Minimum Tank Size:
|Tank Mate Compatibility:
|Livebearers and peaceful community fish
The Swordtail is a delightful livebearer.
There are many beautiful color morphs available. Some are more expensive than others but there are plenty that are affordable and accessible.
These fish do not ask for much in terms of care.
A clean tank, good food, and an environment that resembles their natural home as much as possible is all that they will ever need.
Swordtails are excellent for brightening up an aquascape and bringing life to a particularly boring backdrop.
There is certainly a lot to love about the sensational Swordtail Fish.
What is the most beautiful Swordtail morph that you have ever seen? Let us know in the comments section below…