Do Swordtail Fish Eat Their Babies? And Why?

If you’ve thought about raising swordtails, you probably wondered: do swordtail fish eat their babies?

Both male and female swordtails will eat their babies. Adult swordtails will often mistake their babies for potential food due to their small size.

Swordtail fish are among the most famous picks among fish-keeping lovers. They’re very peaceful and their colors are a beautiful sight.

However, swordtails, like many other fish species, eat their fry. So let’s get to know why they eat their babies, and how you can keep them safe until they’re big enough.

Do Swordtail Fish Eat Their Babies?

It’s common knowledge that swordtail fish is a friendly and peaceful fish species. However, like many other fish species, it’s also common for them to eat their babies.

Swordfish belong to the livebearers family and most of the species in this family don’t have maternal instincts. And as such, they can eat their babies for different reasons.

Swordtails see any living creature that’s smaller than them as prey. This is why they eat their children because, at a young age, their size and movement imitate prey in the eyes of their parents.

And because fish are almost always hungry, they’ll see anything around them as food. You might think that if you feed your fish enough, they won’t have to eat their babies.

But that’s not the case as most of the fish food brands in the market don’t satisfy their hunger. Not only that, you shouldn’t underestimate their hunger. These guys are never not ready for a meal.

So the question is, how can you keep swordtail children safe from their parents or other fish in your aquarium?

How to Keep Swordtail Babies Safe

There are a few ways to keep swordtail fry safe until they’re big enough for the adults to not see them as prey.

Separating the Adults and the Children

The best way to protect swordtail fry is to separate them from the adults until they’re big enough.

By Removing the adult fish into a separate tank, you’ll guarantee the children’s safety and growth. And when the fry are old enough, you can move the adult fish back with them without worry.

Keep in mind that if you have any other adult fish species in the tank, you’ll have to remove them as well. Because as we mentioned before, most fish species prey on their children.

Buy a Breeding Box

Breeding boxes can be a good option to temporarily keep the swordtail fry safe. They’re also not expensive and they can be found in any pet store.

The breeding boxes consist of two parts and a plastic layer that separates the two. The upper part is for the pregnant swordtail fish and the lower part is for the fry to fall into.

The pregnant swordtail is put into the upper part of the box when it’s time for the birth. After the birth, the mother won’t be able to reach the fry in the lower part of the box and they’ll remain safe.

One thing to keep in mind is that if you put the mother in the box too early, it’ll cause stress and birth problems. So make sure to put them in the box when they’re ready to give birth.

When the birth is over, you can now remove the mother from the box and put her back in the aquarium.

Afterward, remove the plastic layer that separates the box parts. This is done to create more space for the fry to swim in.

Keep in mind that breeding boxes can’t house the fry for too long. The space isn’t very big and the water will become stagnant. That’s why you’ll have to change the water regularly.

There’s also a chance that the fry might swim out of the box. So, it would be more convenient if you raise them in a separate tank.

Create Camouflage for the Fry

This isn’t guaranteed to keep the fry safe, but it can work in some cases. Creating camouflage can help hide the fry from the hungry fish in the tank.

You can add lots of floating plants and caves. Bushy and dense plants would be preferable because they create good hiding spots.

Java moss and guppy grass are good options as well. Though it doesn’t guarantee their safety, these options may hide the fry until they’re old enough to live with the adults.

When Are the Fry Ready to Live With the Adults?

If you’ve succeeded in keeping the swordtail babies safe, you’ll probably wonder when it’ll be safe to put them back with the adult fish.

Swordtail fry reach maturity and are ready for breeding after six months. But before you put them back with other adult fish, you have to separate the males from the females first.

To differentiate between them, take a look at their gonopodium, also known as anal fins. The female fins are more round than the males’. Male fins are more pointy and long as well.

Unlike other fish, swordtails don’t change sex so you won’t have to worry about that. However, males are often mistaken for females because the shape of their anal fins can develop a bit late.

That being said, the males do develop their qualities early on, so that should help you with the confusion. You’ll often find them displaying dominant behavior and their bodies are usually thin for their age at that stage.

After separating them, you should keep a ratio of three females and one male. If the males outnumber the females, they’ll start fighting each other for mating.


To sum things up, yes swordtails do indeed eat their babies. But there are ways to prevent that from happening.

While all the methods we mentioned can work, the best, guaranteed option is to separate the babies from the parents.

Raising the babies in a separate tank guarantees their safety, and eliminates any chance, or risk, that they might get eaten.

And of course, a separate tank isn’t the answer alone. The right care and nutrition are also necessary, so make sure to take care of the little ones!