Keeping Tropical Fish: The Colourful World of Swordtail Fish

 

Swordtail fish are among the most popular freshwater fish in the aquarium hobby, beloved for their vibrant colours, peaceful nature, and distinctive “sword-like” tail extension on the males. These striking fish are ideal for both beginners and seasoned aquarists, adding beauty, movement, and charm to any aquarium setup.

In this blog, we’ll take a deep dive into the fascinating world of swordtail fish. You’ll learn about their natural origins and history, how to identify and care for them, what they eat, the best tank mates to choose, and how to successfully breed them at home.

Whether you're starting your first community tank or looking to expand your aquatic family, swordtails are a colourful, hardy, and lively addition worth considering.

Keep reading to discover why swordtail fish continue to win the hearts of aquarists around the world and how you can give them the ideal home they deserve.

Swordtails  / Xiphophorus hellerii

Origins and History

Swordtails (Xiphophorus hellerii) are native to the warm rivers and streams of Central America, particularly in countries like Mexico, Belize, and Honduras. They were first introduced to the aquarium trade in the early 1900s and have since become a staple in fishkeeping communities around the world.

Over the decades, breeders have developed numerous colour variations through selective breeding, making the swordtail one of the most diverse and visually appealing livebearers available today.

What Do Swordtails Look Like?

The swordtail gets its name from the elongated, sword-like extension on the lower part of the male’s tail fin. This feature is absent in females, making it easy to distinguish between the sexes.

Swordtails come in a variety of colours, including red, orange, yellow, green, black, and even iridescent combinations. They have a streamlined body and typically grow to about 4 to 5 inches in length, with males usually being slightly smaller than females.

While not an exhaustive list, here are some of the common swordtail varieties you're likely to come across at your local fish store:

•  Red Swordtail - Bright red or orange body with a matching red tail. A classic and very popular variety.

• Green Swordtail - Olive-green body with dark horizontal stripes. Resembles the wild-type swordtail.

• Pineapple Swordtail - Golden-yellow body with red-orange fins—resembling the warm tones of a pineapple.

• Marigold Swordtail - Yellow to orange gradient body, often glowing like a sunset. Very vibrant.

• Black Swordtail - Solid black body and fins. Sleek, dramatic, and striking in planted tanks.

• Tuxedo Swordtail - Two-toned with a dark back half and bright front—like a fish in a tux!

How To Care For Swordtails

Swordtails are popular among aquarists of all levels—from beginners to experienced hobbyists—thanks to their hardiness and peaceful nature. They are relatively easy to care for, provided their water conditions stay stable and within the ideal range.

Water Quality and Temperature

Maintaining good water quality is vital and can be easily checked with an aquarium test kit. In the UK, where temperatures tend to be cool or fluctuate, having a heater in the tank is essential. Swordtails are sensitive to sudden temperature changes, so using a heater with a thermostat and a thermometer helps keep the water stable and creates a healthy environment for your fish.

Creating Your Underwater Environment

Swordtails thrive in well-decorated tanks with plenty of places to explore and hide. Adding live, silk, or plastic plants helps them feel safe and secure, mimicking their natural habitat. Be sure to include open areas too, so they have space to swim freely and display their playful, active behaviour.

Explore our full range of aquarium ornaments and decorations online, or visit us in-store to find the perfect additions for your setup!

 

Diet – What Do Swordtails Eat?

Swordtails are omnivores, and in the wild, they spend their time grazing on algae, plant matter, small invertebrates, and occasionally fish eggs. To keep swordtails healthy and vibrant in your aquarium, it’s important to provide a diet that closely mimics what they would eat naturally.

What should you feed swordtails? A high-quality tropical flake or pellet makes a great daily staple, providing essential nutrients. Adults do well with one feeding a day, while younger swordtails and fry benefit from two to three feedings to support their growth.

Incorporating vitamin-rich foods into their diet is important for swordtails. We suggest supplementing with nutritious treats like freeze-dried, frozen, or live options—such as daphnia, bloodworms, brine shrimp, plus many more!

These protein-packed foods not only boost their overall health but also help bring out brighter, more vibrant colours. Many hobbyists rely on products like bug bites, which are loaded with essential nutrients.

These treats should be offered alongside their regular daily diet to provide balanced nutrition without overfeeding, which can cause issues in the tank. NT Labs fish treats are also a fantastic option—they stick to the aquarium glass, creating a fun and interactive feeding experience for your fish.

Looking for premium aquarium foods to keep your swordtails happy and healthy? Check out our carefully curated selection [here].

Are Swordtails Messy Fish?

Swordtails aren’t typically heavy waste producers, but having a reliable filtration system is still crucial to keep your aquarium water clean and healthy.

Overfeeding can quickly impact water quality and reduce filter efficiency, so it’s important to feed them appropriately. Regular water testing is also recommended to monitor parameters and catch any issues early.

For more tips on maintaining great water quality, check out our blog on Understanding Your Aquarium Water here…

How do I know if I’m overfeeding swordtails?

If you see long, stringy faeces, it’s a sign of overfeeding. To avoid this, feed swordtails small amounts once a day—only what they can eat within a few seconds. Adjust portions as needed to keep them healthy and your tank clean.

 

Tank Mates – Who Can They Live With?

Swordtails are peaceful and social fish that generally get along well with a wide range of other small to medium-sized tropical fish. Their active nature and calm temperament make them a great addition to community tanks.

Some popular and compatible tank mates for swordtails include (but aren’t limited to):

• Guppies

• Platies

• Mollies

• Zebra danios

• Corydoras catfish

• Dwarf gouramis

• Tetras

• Rasboras

• Rainbowfish

• Otocinclus catfish

• Bristlenose plecos

Avoid keeping swordtails with aggressive or overly territorial fish, as this can cause stress. Always ensure tank mates share similar water parameters and temperament to create a harmonious environment.

Which fish species should I avoid keeping with swordtails?

You should avoid tank mates that are large enough to see swordtails as food or those that are aggressive and territorial toward smaller, peaceful fish.

Some species to steer clear of include (but aren’t limited to):

• Reed fish

• Pictus catfish

• Parrot fish and most other large Cichlids

• Birchir

Choosing calm, similarly sized fish helps ensure a peaceful, stress-free community tank for your swordtails.

For any further advice on possible tank mates for swordtails, pop in store or give us a call on 01204 582105. Alternatively, click here to be taken to our contact information page.

How many swordtails should be kept together?

Swordtails are social fish that thrive best when kept in groups. Ideally, you should keep a minimum of 3 to 6 swordtails together to encourage natural schooling behaviour and reduce stress or aggression. Having a group helps them feel secure and more active in the aquarium.

A good rule of thumb is to maintain one male for every two to three females to prevent males from constantly harassing females. Swordtails also do well with other peaceful community fish, making them a great choice for a diverse tank.

For 3 to 6 swordtails, a tank of at least 50 Liters is recommended. Larger groups or community setups need 100 Liters or more. More space is always better. Be sure to provide plenty of swimming room, plants, and hiding spots to keep your swordtails healthy and happy.

 

Why might swordtails show signs of aggression?

Swordtails are generally peaceful and social fish, but they can occasionally display aggression, usually towards their own species. This behaviour often stems from environmental factors.

Common causes include; overcrowding or a tank that’s too small, which can increase stress and territorial disputes. An unbalanced male-to-female ratio—ideally, there should be more females than males—can also lead to aggression. Additionally, poor water conditions may contribute to irritability and increased conflict.

Ensuring proper tank size, balanced ratios, and clean water helps keep swordtails calm and happy.

Breeding Swordtails

Female swordtails have a rounded, triangular anal fin, while males have a more pointed anal fin with an elongated reproductive organ called a gonopodium.

Swordtails are livebearers, meaning they give birth to free-swimming young rather than laying eggs. Breeding them is relatively easy, and in many cases, they will breed on their own without any special effort.

Here’s what you need to know:

1. Sex Ratio: Keep at least two females for every male to reduce stress on the females.

2. Gestation: Female swordtails are pregnant for about 28 days.

3. Fry Care: Once the female gives birth, it's best to separate the fry into a hatchery or provide dense plants and hides around the aquarium, as adults may eat the babies.

4. Growth: Fry can be fed crushed flakes, baby brine shrimp, or specialized fry food until they are large enough to join the main tank.

 

The Bottom Line on Swordtail Care

Swordtails are a colourful, hardy, and peaceful species that make a great addition to most freshwater aquariums. With proper care—including stable water conditions, a balanced diet, and compatible tank mates—they thrive and bring vibrant life to your tank and offer an enjoyable and rewarding experience.

If you’re ready to add these beautiful livebearers to your aquarium, be sure to create the ideal environment and enjoy watching their lively personalities brighten your underwater world!

Ready to Add Swordtails to Your Tank?

Swordtail fish are a fantastic choice for any freshwater aquarium enthusiast. They’re easy to care for, fun to watch, and bring vibrant energy to any setup. Whether you’re a beginner or looking to add new life to your tank, swordtails are a smart and stunning pick.

Thinking of starting a community tank or expanding your fish family? Visit your local aquarium store or trusted online retailer and bring home some swordtails today!

For more tips on caring for tropical fish and exploring different species, be sure to check out our other blogs here.

A Beginner’s Guide to Setting up an Aquarium | The Best Freshwater Fish For Your Aquarium | Keeping Tropical Fish: How to care for Silver Sharks