The Ultimate Swordtail Fish Guide

“I mean, if you look at it like that, there’s not much to learn about swordtail fish, right? They are… fish!”

This is what my co-worker said to me when I told him that I’ve been working on this article for over a week. After eyeing him down with much contempt, I decided to fight fire with fire.

“Yeah, well… not much!” I replied. “Except that they can give birth to around 100 babies at once, the female can literally just turn into a male in her mid-life, and that swordtails eat their own babies.”

My co-worker was baffled by then, and surprisingly, it felt great to see him so astounded by what I had to say as it proved 2 things:

  • I hadn’t been wasting my time curating information about something that everyone already knew.
  • I had collected cool enough information to interest people into reading about these beautiful creatures.

So, without further ado, I present to you my ultimate swordtail guide. This is the most detailed and comprehensive article on swordtails that you will find on the internet. It has been divided into various chapters, so feel free to browse between those and read a particular one that interests you or one that contains information that might be useful for you in particular.

Here is a list of the chapters that we will be covering in this article:

  • Chapter 1: Introduction to Swordtails
  • Chapter 2: Natural Habitat and Tank Requirements of Swordtails
  • Chapter 3: Swordtail Breeding and Fry Care
  • Chapter 4: Swordtail Diet

How To Breed + Care for Swordtails (Video)

Chapter 1: Introduction to Swordtails

The swordtail is one of the most common aquarium fish around the globe. Although there are many reasons that can explain their fame in the aquarium world, yet the following two are my personal favorites:

  • Swordtails are hardy fish and can live in a varying spectrum of temperature, pH, and water hardness levels.
  • Swordtails are incredibly beautiful and eye-catching, especially with the beautiful “sword-like” elongated anal fin in the male.

In this chapter, I will provide a comprehensive introduction to swordtail fish including details about their:

  • Name
  • Gender differences
  • Live-bearing
  • Size
  • Color
  • Nature
  • Life span


The scientific name of swordtails is Xiphophorus helleri. The word Xiphophorus is derived from Greek and it means “holding a sword” or “sword bearing”. Now, when I initially came across this name, I thought to myself that this must be one aggressive fish!

But I was wrong. Swordtails are one of the most peaceful fish that you will find on the planet. The reason why they are called swordtails is not because they are fighters, instead, it is because of a physical aspect of theirs.

In the male swordtail, the tail fin (also known as the anal fin) is elongated as if it were a sword. This “sword” could grow up to reach half the size of the fish itself! As this is a very uncommon yet dazzling feature found in this fish, scientists and hobbyists decided to name it after this trait.

Gender differences

Swordtail fish are quite fascinating creatures when it comes to gender differences. A lot of people don’t really know that the characteristic “sword” of the swordtail, which is actually an elongated anal fin, is only found in the males. The female swordtail is devoid of any sword and has a non-elongated fan-shaped anal fin. This can make it appear more like some other closely related fish such as the platy.

The female swordtail fish is also slightly larger (it can grow up to 5 inches) than the male (which can grow up to 4 inches) if you choose to ignore the length of the male’s tail. A lot of people are firm believers that female swordtails can mutate in their lives and grow a sword to become a male. Now, this is quite bizarre, but it has been reported by many fish keepers from across the globe. Often, they’d tell you that the reason behind this is that the female is consistently harassed by the males, so she changes her gender.

Although there are many who validate the truthfulness of this mid-life gender swap, yet experts believe that these are only late-blooming males who grow their elongated anal fin (sword) later in their life. That is why these gender-swapping females are never pregnant even during their perceived female stage; because they are actually males!


Swordtails belong to the family of fish known as the “Poeciliidae family”. This is the group of fish that give birth to live babies instead of laying eggs.

In the aquatic world, this is a rare phenomenon as usually mammals like ourselves are known to give birth to live babies. Yet, nature has bestowed this feature in the live-bearer fish as well and swordtails are one of them.

This helps the swordtails to have a great survival ratio for its babies as live-bearers are able to provide maximum protection and care to their baby fish (also known as fry). When the fry are born, they are fully developed and can survive on their own.

Now, before you start assuming this as a “happily ever after” story, let me burst your bubble. The swordtails have a very high ratio of survival during birth for its fry, yet, it is important to understand that like most live-bearers, swordtails would eat their own fry once they are born.

Why, you ask? Because swordtails and all other live-bearer fish have no maternal instincts. That might sound really cruel to you, but your mother swordtail doesn’t really recognize its kids. That’s because she naturally does not have the concept of caring for her babies. As an omnivore (an organism that eats both plants and animals), your swordtail will easily eat its own fry without another thought.

If you want to know more about swordtail breeding, pregnancy, and fry care, you should read “Chapter 3: Swordtail Breeding and Fry Care”.


If you’re considering your swordtails to turn out to be just like rest of the live-bearers, then you’re sadly mistaken. Swordtails are far larger than your average live-bearer fish. The male swordtail can attain a size of 4 inches while the female can grow up to 5 inches in length and that is quite big if you consider other close relatives of the swordtails like the platy that can grow to a maximum size of 2.8 inches.

What’s more; the 4-inch size for males actually excludes the famous “sword” that can attain a size of as much as half the length of the body itself. This can give the male swordtail a total length of 6 inches which is huge according to aquarium standards.

Despite that, the size of swordtails is usually smaller in aquariums as compared to the wild. One can expect that the closed environment for the fish in the aquarium must play a huge role in the overall decrease in its natural size.

This is the reason why your average 10-gallon tank might not be a great fit for swordtails, especially if you are willing to let it breed and then plan on keeping the fry. If you want to keep a community of swordtails, then you should be looking at 29-gallons or above for your tank size. If you wish to learn more about the optimum tank size, requirements, and water parameters for swordtails, you should read, “Chapter 2: Natural and Artificial Habitat of Swordtails”.


Swordtails are mesmerizing animals and that’s the basic reason why they are so popular as pet aquarium fish. They come in a wide variety of colors; out of which green is the most common in the natural waters. Another combination of swordtail that can easily be found in natural waters is red with black tail.

Some common colors of swordtail fish include:

  • Green
  • Red
  • Yellow
  • Golden

You can find a lot of other vivid and eye-catching colors in this fish. Although these colors are not a natural mix which can be easily found in rivers and lakes, yet, these colors have been developed over years of inter-breeding between different closely related species.

It is famous that swordtails can breed with platy fish which are a close relative of theirs. The platy is found in around a dozen breath-taking colors and have passed on a few of those to the swordtails as well.

The swordtail fish rarely have some speckles on its fins. Not only that, you can also find a few breeds of swordtails that have varying types of tails and fin. These variations are rare and often expensive, so if you’re looking for pet fish options that are impressive and can be boasted in front of your gang, then these are your best options.

A couple of common examples of such variations are the hifin swordtail which has a “high fin” and the lyretail which has a tail elongated from both sides like a fork.


The swordtails have a very friendly and harmonic nature. You wouldn’t find these little buddies fighting much as long as you provide them with the sort of healthy environment that they need. The females usually bond pretty well and can be found swimming around, exploring the tank with one another.

The males, on the other hand, might be a different story. A lot of people isolate their swordtail males from the females. This is an effort to curb the rate of reproduction in these fish which can give birth to a new batch almost every month!

But what this does is frustrate the males which, in turn, begin fighting with each other. They would be found chasing the other ones or nipping at their fins. That is why it is advisable to buy only females if you aren’t willing to breed your swordtails. What’s even better is that it’s the easiest thing in the world to spot a female swordtail; they are the ones with no swords as that is a male-specific feature of this fish!

In very rare cases, a dominating bully proclaims himself as the Lord of the tank. This bully can be found chasing innocent younger males who are just at the wrong place at the wrong time. Such aggressive males need to be tended to in time so that the issue can be resolved before it causes great amounts of stress for the other fish.

You can give the bully a time-out by isolating it from the community tank and placing it individually in another one. At times, when you put the bully back in the community tank after such a time-out, the tough guy forgets his role as a bully and lives in harmony with the other fish.

Life span

A lot of people say that fish aren’t very practical pets because they die too early. This is only because most owners never provide the proper environment for fish to thrive in. A swordtail fish which lives in a healthy environment can be expected to live for 3-5 years.

If you are interested in learning the details on the specific conditions in which swordtail fish thrive or the parameters for your swordtail fish tank, you should read “Chapter 2: Natural and Artificial Habitat of Swordtails”.

Swordtail fish usually do not die from aging. In fact, most swordtail deaths occur due to diseases or stress. Being live-bearers, the process of swordtail birth puts a lot of pressure on the little bodies of these fish. Over time, this stress builds up which leads to different illnesses and complications, eventually building up to the fish’s death.

Chapter 2: Natural Habitat and Tank Requirements of Swordtails

A lot of you might be thinking that it is simply a waste of time to read about the natural habitat of swordtails if you’re planning on keeping them as pets. I mean, what good would that do when you’re just going to be keeping them in a tank? After all, they are just fish, right? You would need to buy a tank and pour in some water and the fish will be partying all night to celebrate their existence.

Wrong! Fish are one of those pets that require very specific parameters in their environment in order to live a healthy life. A lot of people have this misconception that pet fish do not live for long but that couldn’t be farther from the truth. Swordtails, in particular, have an average lifespan of 3-5 years. The major reason why they fail to survive for more than a year in aquariums is that fish owners never take out the time to learn about the tank requirements for their breeds so that they can create healthy conditions for them.

Studying about the natural environments of these fish will help us understand better as to what sort of conditions are required by swordtail fish and how we can recreate them in an aquarium.

Swordtail’s natural habitat

Swordtails are usually found in the fresh waters of Northern and Central America. Here, you can find them in great numbers in the wild as they reproduce at an exponential rate. The average female swordtail would attain sexual maturity within 4 months and then continue to reproduce every month of her life as long as she is healthy.

This has increased the number of swordtails in natural waters to a great extent. Honduras, Gautemala, Mexico and other areas which border the Atlantic coast are filled with this fish.

In terms of the type of water body that these fish prefer; they can live in freshwater lakes, rivers, small ponds, and even ditches. Swordtails usually prefer to live in shallow waters which are very thickly planted. The vegetation has many benefits for the fish as it acts as a source of food, a place for hiding, and a natural source of oxygen.

In the wild, swordtails would feed on insects and crustaceans to meet their protein requirements, while plants, detritus, and algae would suffice their vegetative appetite.

Because of such diverse living conditions in the wild, swordtails have attained the ability to endure a plethora of different living conditions.

Aquarium conditions for swordtail fish

In the coming sub-headings, we will be exploring the parameters that one needs to set inside their swordtail aquarium for the fish to thrive and live a healthy life. These include:

  • Tank size
  • Water parameters
  • Plants
  • Bacteria and filters
  • Tank mates

Tank size

Now that we have discussed the natural habitat of the swordtail fish, it is time we analyze the artificial requirements for your swordtails in an aquarium. The first and foremost requirement is the tank itself.

There are mainly 2 reasons why buying a 10-gallon tank for your swordtails isn’t much of a viable option:

  • Swordtails are larger than the other tropical live-bearers. The platy fish, which is a close relative, can attain a maximum size of lesser than 3 inches while the male swordtail can reach up to 6 inches if you consider its tail as well; the complete fish can be half a foot in length! Now, consider that in terms of a 10-gallon tank and you’ll see why it’s not a good option to be keeping these fish in one of those.
  • Swordtails are live-bearers. This means that they give birth quite often, quite successfully, and to quite a lot of babies at once. This will soon overpopulate your tank in no time at all and you’ll be wondering how bad a decision it was to buy a smaller tank. If you’re interested more in swordtail breeding and their babies, you should read, “Chapter 3: Swordtail Breeding and Fry Care”.

A 10-gallon tank would barely be able to hold 3 swordtails in a healthy manner. If you wish to buy more than 3 swordtails or let your swordtails reproduce (which they eventually would, with or without your blessings), you would be needing at least a 29-gallon tank. I would advise buying an even larger one if you have the resources as the more space you provide to your swordtails, the lesser will be their stress and aggression towards each other.

Buying a smaller tank would also lead to stunted growth among the fish. It is quite a famous belief that fish grow larger in the wild as compared to aquariums, but their growth can be even more stunted than usual if the tank size is too small. This might also lead to a lot of diseases. A great number of diseases occur due to stress in fish like the infamous Ich or Ick which can only affect fish which are stressed.

Water parameters

Swordtails are hardy fish; by this, I mean that they can live in a plethora of conditions inside a tank. This diversity in their character has been inculcated through their widespread existence in varying natural habitats.

i) Temperature

The water temperature is very important for all types of fish. One might say that it is of primary importance for any fish’s existence. Swordtail fish thrive in a water temperature ranging between 72-78 degrees Fahrenheit (22-25 degrees Celsius). They can also survive temperatures as low as 65 degrees Fahrenheit (18 degrees Celsius) and as high as 82 degrees Fahrenheit (28 degrees Celsius), though I’d advise you to keep the temperature within the optimum range.

ii) pH

Swordtail fish enjoy living in slightly alkaline waters with a pH range of 6.8-8. This is because the natural waters that they live in tend to be slightly alkaline. Due to their hardy nature, pH doesn’t seem to bother them as much as it might for other fish.

iii) Water Hardness

Swordtails prefer water which is slightly hard, containing some amounts of minerals like the carbonates of calcium and magnesium. On the DH scale, the optimum range of water hardness for swordtails is said to be 1-24 DH.

iv) Toxin Levels

Every fish tank is susceptible to the following toxins:

  • Ammonia
  • Nitrite
  • Nitrate

Ammonia and nitrite are highly toxic and their levels should always be 0 ppm in the tank. Nitrate is only toxic in large amounts so you should maintain it under 50 ppm at all times, although anything under 25 ppm is highly ideal.

In order to curb the levels of these toxins, you need to establish a Nitrogen Cycle in the tank. More on that later in this chapter.

Tank lid

Another important point to consider for swordtail owners is that these fish are extremely adept jumpers. Many an amateur fish keeper has come back home to the site of a couple of swordtail fish that committed suicide by jumping out of the aquarium. For this reason, the water level should be kept a little lower so that it isn’t easy for the fish to jump out. Even then, the tank should be covered with a lid at all times. If you aren’t willing to invest in an aquarium lid, then swordtails aren’t the best choice for you.


There are countless reasons why you should always invest in plants for your aquarium, but these two should suffice for all the serious fish keepers. These plants provide:

i) Hiding places for the newborn fry

In case you did not know, swordtail fish are live-bearing fish; meaning that they give birth to live, fully-developed babies just like most mammals. As most live-bearers do, swordtails can eat their own fry.

If you do not provide a good number of plants inside the aquarium, the baby fry would have no place to hide from the adults. Resultantly, all of them would get eaten.

ii) Source of oxygen and dietary supplement

Plants are a great source of oxygen and will help clean the water as well. This oxygen is definitely useful for the fish and can go a long way in extending their life span. Some types of plants can also supplement the diet of swordtails which is an added benefit.

Types of plants for swordtails

Swordtail fish live in natural freshwater habitats which are thickly planted. This is why the importance of plants increases manifold for keeping them. Broadly, two types of plants are required in a swordtail tank:

  • Bunch plants like Anacharis. This is a freshwater weed which is one of the most famous aquarium plants on the planet.
  • Floating plants like hornworts. A lot of people tend to disregard this type; but it’s important to have a plant like hornworts in your aquarium as they provide excellent hiding places for fry which tend to instinctively swim up to the surface of the water. Without such plants, swordtail fry would be, as the figure of speech goes, “sitting ducks” for the adults.

Useful bacteria

As humans, we are scared of anything that concerns the word, “bacteria”. When we think of this word, we immediately associate it with illness. But bacteria can be extremely beneficial as well, and the bacteria inside aquariums are a perfect example of that.

So, here’s the thing; every fresh water tank is exposed to some fine levels of ammonia which is extremely toxic for the fish. How does this ammonia enter the water, you ask? Well, it’s everywhere! Ammonia is found in fish poop, uneaten food which is decaying, and dead plants or animals.

Some useful bacteria initiate the Nitrogen Cycle inside the aquarium and convert the harmful ammonia into the lesser-harmful nitrites. The latter are then converted into the relatively safer nitrates which are harmless until found in extremely high quantities. Without these bacteria, ammonia levels would rise drastically, resulting in the death of your swordtails.

How to grow useful bacteria in your aquarium?

Now that you know how important useful bacteria are, naturally, your next question is going to be about how you can culture them in the tank. Let me start by telling you that you need to kickstart your nitrogen cycle weeks before you buy your fish!

This is because it takes a lot of time for the conversion of chemical products in the aquarium water, but once it sets into the groove, your fish would be a lot happier and healthier than they would be without it.

As a general rule, it can take 2-3 weeks for the cycle to begin after you introduce ammonia in the tank by methods of decay.

There are numerous ways to kickstart your aquarium’s Nitrogen Cycle. A few of these are mentioned below:

  • Drop some flakes in the tank and let them decay in the water for 2-3 weeks. Get a testing kit and ensure that the ammonia is maintained at 3 ppm for the first week. The complete process can take over a month as the ammonia converts to nitrites and then to nitrates.
  • You can also use a piece of your old and used filter pad and drop it into your new one. This is a faster process as you are kind of “borrowing” bacteria from the used filter pad.
  • Use gravel from an established tank which uses an under-gravel filter. This is also a faster process.

Aquarium filter

Filters are a must-have if you wish to keep your and your fish’s life easy and stress-free. Without a filter, you will have to undertake frequent water changes for your swordtails. Having a filter will help you by getting rid of harmful toxins, decaying food, and waste matter from the water.

Here are 2 filters that can be very useful in the tank for tropical fish.

Uppetool Sponge Filter

This is a simple sponge filter which has received positive reviews on Amazon. It’s easy to set up and users report it to have shown immediate results in the tank. This filter uses both, biological and mechanical filtration which boosts its performance. Sponge filters are always a good choice for any tank which contains fry as they can be sucked-in by other filters.

Polar Aurora 3-Stage External Aquarium Filter

If you’re looking for something more mechanic with a reasonable price, then this is one of your best options. This one is an external cannister filter with 3 different trays for filtration media. The filter is very quiet and has received over a 100 positive reviews on Amazon.

Aggression in swordtails

Swordtails are usually regarded as extremely peaceful fish. Aggression is not that common in them and if they are exhibiting a harsh attitude towards others, it can be mainly due to the following reasons.

  • Your water parameters and conditions are not meeting their requirements
  • Your male to female ratio is not adequate
  • You have a bully in your tank

i) Water parameters and conditions

If swordtails do not receive proper conditions to thrive in the water, they get stressed and agitated. As a result, you’ll start seeing some aggression in the tank. This usually results in the death of many fish as the stress spreads out to others who are bullied.

In order to avoid such a situation, you need to maintain the optimum conditions inside the tank. As mentioned above, these are:

  • Temperature: 72-78 degrees Fahrenheit (22-25 degrees Celsius).
  • pH: 6.8-8 (slightly alkaline)
  • Hardness: 1-24 DH (slightly hard)
  • Tank size: 10 gallons if you have only 2 swordtails; 29 gallons if you have 5-6; a lot more if you plan on keeping the fry
  •  Ammonia levels: 0 ppm
  • Nitrite levels: 0 ppm
  • Nitrate levels: Below 50 ppm at all times, 25 ppm is ideal

ii) Male to female ratio

Swordtail fish are live-bearers and reproduce at an insane rate. A healthy female fish can give birth to a batch of 10-100 swordtails in one pregnancy that lasts only about 28 days. To avoid overcrowding their tanks, many fish keepers isolate both genders from each other. This allows them to control the mating process and is the only method of doing so.

But the problem that this creates is that the male tank gets too aggressive while the female tank seems to be having the most peaceful time. What you need to do is have a safe male to female ratio which keeps the aggression of the males and the stress of the females down to a minimum.

The optimum ration for male to female swordtails in a tank is 1:3 or 1:4. This means that for every male swordtail, there should be 3-4 females. Having lesser number of females causes a lot of stress on the remaining ones as the males would keep chasing them for attention and reproduction. This would stress them out and eventually kill them.

On the other hand, if you do not wish to reproduce your swordtails at all and want to buy a single gender, then you should always go for females. The ladies get along pretty well and go for peaceful “walks” around the… urm, aquarium!

iii) Swordtail bully

Although this is not very common, but you might end up with a swordtail bully in your tank. You need to first understand that swordtails will acquire a bullying attitude only when they are under stress. To help all the other fish who are a subject to bullying, you need to help the bully itself which is under stress.

For this, you should check the water parameters and conditions for your tank. Refer to the “Water parameters and conditions” subheading in this chapter for the optimum tank conditions.

If this does not solve the problem, you need to isolate the bully into a separate tank. This “time out” technique is very useful as the bullies tend to change their attitude once they are returned into the community tank.

If both of these options don’t work, you might have to isolate the bully completely or sell it to a pet shop.

Tank mates for swordtails

Swordtails get along with a lot of other fish. In general, the following points should be considered before keeping two fish together in the same tank:

  • Relative size: You can only keep such fish in the same tank as your swordtails that have a comparable size to it. Bigger or smaller fish would bully or become a subject to bullying respectively.
  • Optimum tank conditions: Even if the fish that you keep together are hardy, you need to keep such breeds which have similar optimum conditions like temperature, pH, and water hardness.
  • Overall behavior/character: Some fish just aren’t very sociable and like staying only with their own kind. Some of them must be kept in complete solitary confinement.

With that being said, the following fish can be kept with swordtails:

  • Angelfish
  • Kribensis
  • Kuhli loach
  • Emperor tetra
  • Danios
  • Mollies
  • Platys
  • Tetras
  • Rasboras
  • Rainbowfish
  • Gouramis
  • Plecos
  • Corydoras Catfish
  • Clown Loaches
  • hardier Tetras

Chapter 3: Swordtail Breeding and Fry Care

In case you have bought (or are plan on buying) swordtails for your aquarium and you still don’t know, then this is going to be a bummer; swordtails reproduce like crazy! You might have come here thinking that you’ll learn how to make them breed, but what you need to learn instead is how to stop them from breeding. Because, picture this; you have 3 female swordtails in the tank and each one of them can give birth to fry ranging from 10-100 in number every month. Do the math and you’ll realize that you would soon need a private sea to contain all the swordtails (I might be exaggerating a bit!)

Here’s what you need to know about swordtail breeding and fry care.

Swordtails are live-bearers

Before anything else; you need to understand the fact that swordtails belong to the group of fish known as live-bearers. These fish give birth to live babies from the mother’s womb instead of laying eggs. This increases their rate of survival manifold as the mother is able to provide maximum care for the fry up till the point of birth.

Adult swordtails eat their babies

Now to the second most important point; even if your swordtails give birth to dozens of babies at a time, it won’t make much of a difference if you do not take any precautions as the adults would eat the fry.

You might feel like this is the most barbaric thing that you’ve heard, but it’s pretty common in the fish world and most live-bearers do the same. In natural water bodies, the fry are swept away from their parents right after birth due to water currents. The parent swordtails never actually meet their babies in nature.

Many believe that this is the reason why swordtails do not have any maternal instinct and will gobble down their own babies as a potential source of food.

Pregnancy and the process of birthing

The total gestation period of a swordtail fish is around 28 days. The process starts when males release their sperms from the elongated sword-like anal fin known as the gonopodium. The female does not have an elongated anal fin or “sword” hence this structure acts as a distinguishing character between both the genders.

The female can store the sperms from the male for up to 6 months and can undergo numerous pregnancies with a single insemination. This is why most female swordtails that are bought from the pet store are already pregnant and give birth soon after arriving in their new aquarium.

Once the female is pregnant, it will show the following signs of pregnancy:

  • Its abdomen will start swelling up as the fry grow inside the mother’s body. With every passing week, the under side of her body will swell more and more and attain a square shape by the time she is ready to give birth.
  • The female will also have black spots on either side of her anus. This is the gravid spot of the pregnant swordtail and is formed by the eyes of the babies pressing against the mother’s scales (or so it is hypothesized).

Usually around the 28th day, the pregnant swordtail fish gives birth. Right before the birthing process, the pregnant swordtail might appear lethargic and would seem to be wanting some isolation from the community. A lot of fish owners have reported that their pregnant swordtails hide in plants or caverns at this time.

The birthing process can occur in a single or many batches. At a time, swordtails can give birth to 10-100 fry which would be fully developed to survive on their own. They might take a few hours to start moving, but once they do, they’ll be okay to live independently as long as they are safe from the adults.

Swordtail fry care

When you buy a pet, you simultaneously take on the responsibility of a parent. Naturally, when your pet swordtail gives birth to fry, you need to play the role of a hero and save those little dudes from being eaten up by their own parents.

To do that, you can try the following options:

  • Use a heavily planted aquarium with bunch and floating plants. These provide adequate hiding places for your fry and would keep them safe from the adults. Without plants, all of them would soon be eaten.
  • Keep a separate baby tank (preferably 10 gallons) for the fry. You can isolate the mother in this tank right before she gives birth and place her back in the community tank as soon as the babies arrive. After that, you should leave the swordtail fry in the baby tank for the next 2-3 months until they are too big to fit in the adult swordtail’s mouth. Once they attain that size, you can place them back in the community aquarium.
  • You can also use a breeding trap which is basically a case that is placed inside the aquarium. It contains small holes which allow the fry to move across them but stop the adults from doing so. You can either keep the adults inside the breeding trap and let the fry swim in the tank or do it the other way around.

Chapter 4: Swordtail Fish Diet

Diet plays a huge role in the well-being of an animal. One of the best things about owning fish is that they are relatively easier to keep in this regard as their diet requirements aren’t too complex.

Swordtails are omnivores

The first and foremost point to understand for swordtail fish diet is that they are omnivores. This means that they require both plants and animals in their diet and explains why they eat their own babies.

In order to provide your swordtails with a balanced diet, you should ensure that they receive enough carbohydrates and proteins to survive. For that, you can use artificial, live, or frozen food products.

Fish flakes

In any swordtail fish diet, fish flakes should be an integral part. Good quality fish flakes are available in pet stores and online and will contain all the necessary nutrients for your fish to live a healthy life.

Tropical fish flakes: Out of a whole bunch of options for fish flakes that you can find on Amazon, this one seems to be a quality option. The flakes contain vitamins and probiotics. They also contain salmon fish as a protein product which would help provide your swordtails with a good all-round diet.

Vegetables for swordtail diet

Vegetables are highly important for swordtail diet. In nature, swordtails substitute them by feeding on algae but that isn’t a viable option for aquariums. Instead, you can feed them the following vegetables after properly blanching them in boiling water:

  • Zucchini medallions
  • Cucumber medallions
  • Shelled peas
  • Broccoli

Live food for swordtails

If you wish to keep your swordtail’s diet as close to nature as possible, then you might be considering to feed them some live food. Well, in that case, a few favorites for swordtails include:

  • Daphina
  • Blackworms
  • Bloodworms
  • Brine shrimp
  • Mosquito larvae (These are illegal to culture in many areas around the world.)

A lot of these live food options can be bought as frozen foods from pet stores and they work equally well for swordtails. Make sure that you defrost all your frozen foods before dropping them in the tank as you wouldn’t want your swordtails to eat something hard and icy as it might hurt them.

Swordtail fry diet

So, here’s some good news; swordtail fry eat the same food as their parents and don’t have specific food requirements. This means that you can feed them the same fish flakes that you feed the adults. The only problem that they would have is to ingest the flakes which are usually too big for their mouth.

For this, you can grind the fish flakes to a finer powder with each flake ground to quarter the size of your pinky nail.

If you’re willing to go the extra mile and want to get the healthiest swordtail fry with the brightest coloring, you should go for live foods like brine shrimp and microworms along with regular fish flakes. Egg yolks are also a good option as a baby swordtail diet.


Swordtails are beautiful fish and it is no wonder why they are so famous as a pet option. It doesn’t matter if you are a beginner or experienced aquarist, swordtails should suit you perfectly. Although this is quite a comprehensive and detailed article and contains all the information on this pet, yet I understand that it can be hard to remember all of this. For this reason, I’d advise that you bookmark this article and come back to it whenever you need to clarify any particular point about your swordtails.

Related questions

What kind of fish can live with swordtails? Swordtails are peaceful animals and usually get along with other fish that have a similar size to theirs. Some famous options for swordtail tankmates include mollies, platies, tetras, Angelfish, and Gouramis.

Is swordtail fish aggressive? Generally speaking, swordtail fish are not aggressive but can exhibit such an attitude under specific unfavorable conditions. These include inadequate water parameters, improper male to female ratio (you should keep 1 male for 3-4 females), and overcrowding.

How long is a swordtail fish pregnant for? The total gestation period of a swordtail is usually 28 days, although it may vary from fish to fish or due to external conditions. It is often hard to predict when the gestation period begins as the signs of pregnancy (swollen belly and the appearance of a dark gravid spot) become apparent a couple of weeks into the pregnancy.

Do swordtail fish eat their own fry? They most certainly do! Swordtails are live-bearers which means that they give birth to fully-developed babies and not eggs. Like all other live-bearers, swordtails are devoid of any maternal instincts and can eat their own babies. Many believe that there is no concept of parenting in swordtails because in the wild, water currents take the fry away from the parents right after birth which is why they never really get to see their babies.


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