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Swordtail Fish Overview, Care, Tank Setup & Tank Mates

Swordtail fish are colorful species that make great additions to any passive community aquarium. They add interest and color to your tanks and are ideal for both novices and experts alike.

Dedicated breeders are developing iconic swordtail varieties, most of which are instantly recognizable even to those who’ve never owned an aquarium.

Although they’re reasonably low-maintenance, these require more than just a bowl and some food. You do have to keep the temperature and water conditions within a particular set of parameters.

One can easily mistake them for guppies or platies, but they are different.

We’ll discuss the complete swordtail fish care guide below.

Species Overview

Green Swordtails (Xiphophous helleri) are small freshwater fish originating from North and Central American waters.

Their natural habitat stretches from Central Mexico in the north to Honduras in the south, but these days they can be found in nearly every place on earth – thanks to dedicated pet stores worldwide.

Most varieties prefer to live in fast-flowing rivers and lakes with lots of greenery. They can be found in other habitats that may be easier for fishkeepers to replicate, ranging from slow-moving drainage ditches to smaller ponds.

Because their natural habitat is incredibly varied, swordtails have developed hardy bodies with robust immune systems and can adjust to a wide range of conditions in the aquarium.

They will do well in most water conditions, so long as you don’t deviate too further away from the recommended settings.


Swordtails have an uncanny resemblance to guppies and platies. Their colors tend to vary dramatically.

Those found in the wild will have red and yellow streaks on either side with a generally olive green appearance.

For this reason, locals aptly name wild swordtails after the color of their skin; examples include Green Swordtail and Red Swordtail.

Some rare varieties have been observed to have vibrant and colorful spots along with their fins. Under captivity, breeders have selectively bred them to produce different types of fins and exciting colors.

The name swordtail itself comes from the unique appearance of the males. Males have protruded extensions that grow along their lower tail fin lobe, giving the formation of a ‘sword’.

This property is unique to males only, and females have not been observed to have caudal fins with similar protrusions.

The tail is arguably their most striking physical characteristic, although it doesn’t serve an apparent purpose.

The male’s tail accounts for 1/3rd to 1/4th of their total length. Swordtails in the wild have more majestic ‘sword’ tails reaching over 6 inches in length.

Males will typically reach 6 inches in length, but females could be an inch bigger.

Behavior & Temperament

Swordtails are ideal for novices because they are generally peaceful, and lively, swim in loosely grouped schools, and thrive in communities of other peaceful small fish. Although they live in groups, they’re not known as shoaling species.

Males have known to be aggressive towards one another to mate with females, so make sure that females outnumber them by a ratio of 4 females to 1 male.

They may become somewhat shy when kept in the same tank with active fish species and may try hiding in decorations and plants. Their favorite spots in the aquarium are the upper and middle levels, rarely swim below. If you provide them with a large enough tank, they will become much more active.

These are so active that they’ve known to jump out of the tank. If you don’t want your swordtail drying up on the carpet next to its tank, make sure the lid is tightly kept on the tank at all times. Also, ensure that the tank doesn’t have any bullies and that the water’s conditions are favorable enough for all species.

Ideal Tank Conditions

One swordtail needs at least 15 gallons of space in the tank. Double that too, at least 30 gallons if you plan on breeding them

Although they’re not particularly big, they do need lots of space to swim. Each additional one requires roughly 5 gallons of extra water for maximum comfort. The water needs to be kept at temperatures between 73 to 78 ° Fahrenheit at a pH of between 7.0 and 8.5. The hardness level of the water can vary between 1DH to 24DH.

Ensure that the tank conditions are not changed too abruptly; otherwise, it could cause health problems.

Use an aquarium heater to maintain the correct temperature if the room isn’t at the right temperature. You will have to partially change 10% of the water every week or about 25% of the water every two weeks.

Although they live in fast-moving waters, like rivers, streams, and mountain creeks, you don’t need a pump to move the water around the aquarium. A filter outlet should provide them with enough current.

Go for the most oversized filter you can buy for your swordtail. A good choice would be HOB filters because they create currents that they will enjoy.

Tank Setup

Their original habitats are densely populated with vegetation and lots of rocks. It can easily replicate with stones and plants. The plants provide them with shade from sunlight and shelter from other fish and flowing water. Although swordtails have been found in brackish waters, this is relatively rare and can hurt their chances of living a healthy life.

Because they rarely swim to the bottom of the tank, you don’t have to worry about substrates unless you have other species that do lurk at the bottom.

A good combination would be to use bogwood and rocks to mimic the natural habitat in your aquarium – they also double as excellent hiding spots for your swordtail. Spread plants around the aquarium, but leave enough space for active swimmers.

There are various plants to choose from, including Java Fern, Anubias Nana, and Java Moss. While you can make do with fake plants, your tank is missing out on the benefits of live plants.

Swordtail fish in aquarium

Tank Mates for Swordtail Fish

Swordtails are peaceful species and rarely show aggression toward other fish, but they have been known to pluck the tails and fins of veil fish. Older males have been known to attack others, but only in cramped aquariums. They have been seen living alongside platy fish in the wild, making them an obvious choice for your tank.

Other species include Dwarf Corydoras, Otocinclus, Neon Tetra, Rosy Barbs, Angelfish, and Zebra Loaches. Some of these fish like to hang out in the middle portion of the tank, which also happens to be the spot where swordtails swim the most – so make sure your tank has enough swimming space for everyone.

As a general rule, do not keep aggressive species in with them as they will attack them. It means no Convict Cichlids or Jack Dempseys. Swordtails don’t typically encounter predator fish in the wild.

You can also add a few invertebrates here, including apple snails and ghost shrimp.

Food & Diet

Swordtails are omnivorous species that will eat just about anything, including commercially prepared flakes, algae, as well as brine shrimp, freeze-dried worms, and tubifex.

But you can provide them with dried foods for a nutrient-rich diet. Feed them with some vegetables as well to give enough giber, so it helps with digestion.

Algae wafers are an excellent choice because they provide enough nutrients. You can also add leftover vegetables to your home.

These like to eat 2 to 3 times a day. Just don’t overfeed them because it could adversely affect the tank’s settings. Please do not feed them more food than they can eat within a few minutes. After your fish have done eating, remove any leftover food to get broken down and causes pollution.

Fish specialists advise sticking to a routine. This way, your swordtails will know when to eat and become more active during feeding times.

Breeding Guidelines

Baby swordtail fish with adult
Baby Swordtail fish with an adult

Swordtails are livebearers, which means instead of laying eggs, they give birth to live fry that are big when born and ready to swim. Like most livebearers, they don’t need much prodding to populate the tank. Any tank containing males and females will quickly fill up with fry; hence it is recommended to buy large enough tanks to accommodate everyone.

Fish specialists recommend adding more females than males in the tank to encourage spawning. During spawning, males will swim over to the females in their efforts to mate with them. It can be a stressful experience for females and could quickly overwhelm them.

How to know if a Swordtail Fish is pregnant?

Once the egg is fertilized, it will take around six weeks for the mother to give birth to her first batch of fry. She will give birth to dozens of fry at a time, with the possibility of giving birth again in the coming weeks, without the presence of a male.

Pregnant swordtails develop swollen bellies and show a dark gravid spot that is easy to identify. They will often struggle to move around the tank. Before birth, they will feel extremely tired and may not be able to eat.

Taking Care of Fry

Like most freshwater fish, swordtails lack parental instinct and will eat their own young. It is recommended to separate the parents from the fry.

If you don’t have an extra tank, you can add more hiding spots in the form of dense vegetation and decorative items. Ideal tank conditions for fry are almost the same as those for their parents. Make sure that the nitrite, ammonia, and nitrate levels are at 0 ppm.

However, the good news for breeders is that swordtail fry is low-maintenance and only needs protein-rich food. Fry needs a lot of proteins when they’re firstborn. It means frozen and live foods like daphnia, brine shrimp, and bloodworms, along with dried foods.

Juveniles are not big enough to eat and digest adult food. But you can provide them with liquid food that is readily available from pet stores. You can also feed them powdered fish flakes and live worms.

Some fishkeepers convert boiled egg yolk into powdered form and feed it to the fry. It provides the juveniles with an immediate source of minerals and nutrients.

The growth rate of juveniles can be incredibly slow at times, but if you want them to grow faster, change the water every few weeks and provide them with a good source of protein.

It will take around 4 to 6 months for juvenile swordtails to achieve adulthood and need to be safely kept away from adult fish until they’re large enough not to be viewed as food.

When they’re fully grown, they won’t fit into an adult’s mouth.

If the fry don’t move at all after birth or are sinking below, it’s a sign they were born premature and could not consume their yolk.

To grow swordtail fry, you need to rest and sleep for several hours at a time in a peaceful environment. Ensure the aquarium lights are on because the light rays will prevent them from developing a risk of deformities during growth.

Preventing Fry from Dying

To increase your swordtail fry’s chances of staying healthy and alive, do the following:

Regulate the water parameters to prevent complications and take immediate action when the tank conditions deteriorate.

Please provide them with a well-balanced diet that contains a mix of proteins and vegetables. Do not overfeed them and remove the leftover food once they’ve had their fill.

Buy a larger tank because overcrowding increases their risk of stress and could cause them to die.

It is common for swordtail fry to get caught up in the aquarium filter and die if they are not covered. Cover the filter with a sponge filter to keep the juveniles out of danger.


Despite being resistant and hardy to diseases, swordtails are under threat of the following conditions:

White Spot or Ich

Ich is a common disease affecting swordtail fish. It appears on their fins, gills, and bodies as white spots that look like grains of salt. It usually happens because of poor water quality that can quickly treat with medication from your local pet store. However, ich is a sign of something wrong with the tank. It could be temperature, dirty filters that haven’t been cleaned out yet, or an infectious outbreak.


Dropsy is a sign that your swordtail fish is suffering from an underlying problem. It happens when they bloat up in size. Bloating is primarily caused by the buildup of fluids along body cavities and tissues. The best way to treat dropsy is by separating your fish to contain the disease. Salt treatment also works well. Add one teaspoon of aquarium salt per gallon of water.

You will need to provide them with a healthy diet for a speedy recovery, including flake food and pellets.

Tail Rot

During this disease, your swordtail’s fin appears ragged and torn. It can cause by poor water quality but could be a result of aggression from other fish. Tail rot is a symptom of bad water conditions and can be treated by regularly monitoring the water’s parameters like temperature, hardness, pH, and more.

Treatment requires fish antibiotics and increasing the temperature to around 80 ° Fahrenheit.

Where to Buy?

Most pet stores have many varieties of swordtail fish for sale. But if you want to buy rarer species, you may have to look for them via online stores and internet forums for specialist breeders and hobbyists. They’re not very expensive and usually only cost about $3 per swordtail fish.


Swordtail fish are peaceful and make great additions to any aquarium. Novices will have to be extra careful with the water’s parameters, maintenance, and area cleanliness. You could end up with more fish than you can handle because they mate frequently.

All in all, swordtail fish are ideal for beginners and give you the perfect headstart in the world of fishkeeping.