How To Care For Pregnant Swordtail Fish?

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One of the most vulnerable times in a fish’s life is during her pregnancy. So, if your Swordtail Fish is pregnant, be ready to care for your pregnant Swordtail.

To take care of a pregnant Swordtail Fish, all you need to do is provide the Swordtail with a nutritious diet, maintain water temperature to 80° F, pH of 7-8, and water hardness to 5-25 dGH. Additionally, a 10% water change every other day is a must. This will ensure that both the pregnant Swordtail fish and the babies growing inside the fish are healthy.

You might be worried about how to take care of your pregnant Swordtail fish. But, if you read the following article, you’ll feel a bit relieved. It’s because I’ve compiled my experience tending my pregnant Swordtail.

Now, let’s get started.

How To Know If Your Swordtail Fish Is Pregnant?

Your Swordtail fish, once matured, is pregnant throughout her life. Thus, if you are doubtful whether your fish is pregnant or not, she most probably is!

If you don’t know her pregnancy signs, I will explain them to you. Bear in mind that Swordtails are livebearers; so they give birth to fries directly without laying eggs.

  • Firstly, your Swordtails’ belly will gradually increase in size as time goes on.
  • Secondly, your Swordtail has a gravid blue spot near her anal fin. This is the growing uterus pressing against her thin skin.
  • Thirdly, the eyes of the fry are visible from the gravid spot. This is the surest sign of pregnancy.
  • Another surest sign of pregnancy in a Swordtail is a square belly. This view is opposed to the theory that pregnant Swordtails have round bellies.

Is Your Swordtail Fish About To Give Birth?

Now, you have positively detected your Swordtail is pregnant. But, how will you know when she is about to give birth?

Signs your Swordtail is about to give birth:

  • First, you need to understand that the gravid spot becomes darker along with her pregnancy. So, the darker the gravid spot, the nearer to labor your Swordtail is!
  • Second, your Swordtail starts to form a square-shaped belly. This is a sign that your Swordtail is near her labor.
  • Third, your Swordtail stops swimming around, loses interest in food, and lies down in the gravel. She will hide behind plants and decorations to get ready to birth her fry.

Taking Care Of Your Pregnant Swordtail Fish

Your Swordtail is pregnant roughly for 28 days. And during this time, you have to properly care for your Swordtail. Else, your Swordtail might get an abortion too. 

Abortion, in a Swordtail, is like human abortion but is done by the female Swordtail on a small scale. Abortion, in simple words, means a pregnant Swordtail giving birth to dead fry. 

Let me not worry you because the birth of dead fry (abortion) in Swordtail is rare. However, you must do your part to ensure a healthy mother and healthy babies at the end of pregnancy!

Care To Feed Your Pregnant Swordtail Fish

Thinking of your Swordtail and the fry growing in her belly, you might end up overfeeding. This is a common mistake that novice Swordtail owners make!

Of course, your Swordtail needs a good diet to sustain herself and her growing babies. However, she cannot eat much as fry takes up her space. 

You should, thus, provide your pregnant Swordtail 3-4 tiny portions of meal a day. Don’t overload her. A small pinch of food 3-4 times a day is enough.

More food might go wasted in your tank, fouling your tank.

Live food like brine shrimp, bloodworms are good for your pregnant Swordtail. She might like high-quality flakes too. Spirulina flakes are also brilliant for your pregnant Swordtail.

Occasionally, you can provide lettuce, peas, and daphnia too.

Hey, you can try this! Give brine shrimp as breakfast, flakes as lunch, spirulina in the afternoon, and freeze-bloodworms as dinner. 

To sum up, you should make sure to give tiny portions. Also, don’t forget to create a variation for nutrition!

Prepare Separate Breeding Tank

I recommend you to get a separate gestation tank, especially during your Swordtail’s late stage of pregnancy. Trust me, your Swordtail will thank you for this.

A separate tank has benefits like:

  • The male Swordtail will not harass pregnant Swordtail.
  • Your pregnant swordtail will not have any tension regarding birthing her babies.
  • There is a case of adult Swordtails eating the newly birthed fry. This can be prevented by a separate tank.
  • The mother Swordtail will have time to take a rest after birthing babies.

You can use a tank divider. But, it’s better to get a separate tank for your pregnant Swordtail. There will be fewer problems using a separate tank.

Actually, 2 separate tanks should be prepared. One for the mother. One for her baby fry.

Or, you can get a breeding box. The breeding box is useful for the fry as it can come out on its will. But, this might stress out your big pregnant Swordtail who has limited space to move around.

Large Tank Space

Pregnancy is hard but labor is even harder. So, to make a stress-free environment for your pregnant Swordtail, buy a large tank of 40+ gallons.

This may seem a bit too much. But, I made the mistake of overcrowding my pregnant Swordtails. This resulted in the death of half of the fry. (I’d kept 3 pregnant Swordtails in a 20-gallon tank.)

You can keep one Swordtail in a 15-gallon tank.

One male in your tank will impregnate many females.

Suppose, three of your Swordtails are impregnated by one male. So now, you need a 40+ gallon separate tank for your 3 pregnant Swordtails. 

It’s even better if you buy a separate large tank for the fries. One Swordtail will birth 80-100 babies. Thus, you need to buy a tank of 30+ gallons alone for the fry.

Maintain The Quality Of Water

Perhaps, the most important factor for your pregnant Swordtails’ good health is the water parameter. Any fluctuation in water parameters can stress your pregnant Swordtail.

Once you have brought the new 40-gallon tank, maintain the water parameter as follows:

  • A Temperature of 74-80 degree Fahrenheit
  • pH between 7.0 – 8.4
  • 10% water should be changed every week. 25% water changed every 2 weeks.

You can maintain temperature with a heater, pH with baking soda. (You can research how to balance pH.)

Once you maintain these water parameters, shift your pregnant Swordtail in this tank.

Care To Place Lots Of Plants For Pregnant Swordtail

Although you have shifted your pregnant Swordtail to a separate tank, she might still feel stressed and not give birth.

If this is happening, try to plant some aquatic plants. Plant some Hornworts, will you? Actually, any aquatic plant with hiding space will do!

Usually, pregnant Swordtails birth behind plants so that her fry is well protected. She will feel like she is in the wild again. Plus, the darkness from plant shadow will balance her sleep habit.

When Should You Separate Your Pregnant Swordtail?

Long-term isolation is bad. That’s why you should separate your pregnant Swordtail from your community tank only after she has shown signs of labor or late pregnancy.

Or, you can keep your pregnant Swordtail in a separate tank on her 27th day of pregnancy.  Calculating that pregnancy duration is 28 days, pregnant Swordtails go to labor around the 27th day of pregnancy! 

Maybe start earlier? You can keep your pregnant Swordtail even starting from the 25th day. The males will stop harassing her. Moreover, she might feel relieved to give birth too.

Delivery Time Of Pregnant Swordtail Fish

The delivery time of a Swordtail lasts for an average of 6 hours. Sometimes, when mother Swordtail is having difficulty, it might take 12 hours.

In some cases, Swordtail will deliver a few babies, stop her delivery, and won’t start delivering, only resuming after a few days.

Sometimes, your Swordtail doesn’t give birth after 24-48 hours of keeping in a separate tank. Your Swordtail might not have mature fry. Thus, you can increase the temperature of your tank slightly to mature her fry.

After your Swordtail gives birth, return the tank temperature to normal.

Isolate Even After Birth

Your pregnant Swordtail needs to rest after giving birth. A resting time of 24-48 hours is necessary. Then, you can shift the female Swordtail in your community tank.

Moreover, cannibalism is well seen in livebearers such as Swordtail fish. The mother will readily eat up her babies without any remorse. Thus, isolating fry and mother Swordtail is important!

You should keep a separate tank for your fry. After birth, separate the fry in your fry tank and keep the mother Swordtail in the same tank.

Common Mistakes While Giving Care For Pregnant Swordtail

You might end up giving all your care to your pregnant Swordtail. But, here are some mistakes you might make while caring for your pregnant Swordtail.

Not Getting Separate Tank For Fry

You might think empathy runs in Swordtails. I mean, Swordtails are peaceful. But, they have no remorse for their own kind.

Thus, you might want to get a separate tank for your new fry. Otherwise, the female Swordtail might end up eating her own babies.

If you can’t get a new tank for fry, maybe get a tank divider? Then, separate the female Swordtail from her fry. This is usually done by people who didn’t have time to set up a separate tank for fry. 

After 2 resting days, you can return the female Swordtail to your community aquarium. Then, you can remove the tank divider and give the whole tank to your fry.

Over Crowding

Even one Swordtail needs 10-gallon space to swim around. Now, think of pregnant Swordtails and how stressful they might feel in a congested tank.

Thus, provide a large tank space for her to swim freely and feel stress-free!


Pregnancy time is vulnerable. I made the mistake of not keeping pregnant Swordtails in a large tank. This resulted in the death of some of the fry (abortion of my female Swordtail fish).

Thus, you should give constant attention to details in your Swordtail.


How Many Babies Do Swordtails Bear?

A Swordtail bears around 80-100 babies in a single pregnancy. However, there might be the death of some fry due to the stress on pregnant Swordtail. 

Why Is My Swordtail Not Giving Birth?

Stress, water parameters, and immature fry may be the reason why Swordtail delays their pregnancy.

Closing Words

I hope you learned how to take care of your pregnant Swordtail through this article. It is not difficult to care for a pregnant Swordtail but negligence isn’t a question either. I’m sure you are an empathetic person who will take care of your pregnant Swordtail’s health.