Are Swordtail Fish Aggressive?

Are Swordtail Fish Aggressive?

Swordtail fish are a fantastic choice for any aquarium. They’re pretty easy to maintain and don’t require much effort.

Swordfish are sociable and love to be around other fish contacting large groups. However, Are Swordtails aggressive?

Swordtails are peaceful fish. However, some circumstances may cause these fish to become aggressive. For example, if there are a lot of males around when they mature, they might get into rivalries. Pregnant fish can also be violent.

In this article, we’ll explore why swordtails might get aggressive and what you can do to minimize this behavior.

Do Swordtail Fish Get Along? 

By nature, swordtails are docile and non-violent. However, when they reach sexual maturity, like most creatures, they can become aggressive.

It’s preferable to keep them in a five or six fish group, with only one male among them.

If you want to house your Swordtails together with other types of fish, catfish are an excellent option. They aren’t only friendly, but they also have similar water requirements.

However, swordtail fish can become aggressive and territorial, even though they are generally docile.

We had prior contact with the fish and their aggressiveness and territoriality at least once or twice.

Several things influence swordtail fish aggression and territoriality. When their requirements aren’t met, it’s natural for swordtails to act this way like most other livebearers.

What Are the Symptoms of Aggression Occurring?

When fish become aggressive, there are several warning clues. The following are some typical behavioral patterns that reveal an aggressive swordtail:


The Swordtail fish sometimes pursue other fish in the tank and even attack them.

This especially occurs when a new fish is introduced into the aquarium, and the old one wants to show its dominance.

Another primary reason for swordtail fish to chase each other is due to their mating dance, which includes attention-seeking.

A swordfish will go around looking for females to choose as a mating partner. When they find the one they like, they start fighting and chasing other males in the tank to attract the female attention.

Although this appears to be an act of aggression, it has no ill effects. However, the constant chasing and harassment may lead to the death of weaker fish.

When swordtails become aggressive, they tend to flare their fins and gills. They may seek refuge among the vegetation or other tank decor items, or they could sit at the bottom of the aquarium.

So, if you notice that your swordfish is exhibiting the above symptoms, it’s a good time to step in and mediate.

Fin Nipping

Fin nipping is when your fish bites the fins or tails of other fish. This is a common occurrence among fish, no matter how big or little the other fish are.

Fin nipping can cause the fish’s life to be in danger because when fish are harassed, they become nervous and more prone to disease.

I’m sure it seems natural, but if your fish keep repeating the behavior over and over, it’s an issue because it shows that they’re frightened.

What Causes Swordtail Aggression & How to Stop It?

Swordtails are typically observed swimming peacefully in the tank with other fish.

However, if your fish are hiding or chasing one another about, you most certainly have an aggressive fish on the loose because of the following reasons:

1. Lack of Space

Swordtails like having a lot of space to swim about in, and if they feel cramped, it can lead to aggression.

When the tank is full, stronger Swordtails will establish their territorial lines consequently, any fish that goes through its border is in danger.


Swordfish require a large amount of area, and you should give them as much as feasible.

Keeping your fish in the properly sized tank will make them happy and not feel cramped or harassed.

A Swordtail requires at least 15 gallons of water, this way, they won’t start chasing each other about.

2. Pregnant Female Swordtail

When pregnant, swordtails will be aggressive. Female swordtail fish are often very protective of their young (babies). If you observe your female swimming around attempting to keep other fish away, she is probably protecting her young.


The best approach when dealing with a pregnant swordfish is to station her in a separate tank or give her an aquarium of its own.

It will be less stressful for her, and she won’t have to compete with other fish for food or space.

3. Male-To-Female Ratio

Keeping a proper male-to-female ratio is critical. As the number of male fish in a tank increases, the chance that they will fight rises.

This makes sense because if you have two or more males in the tank, they might fight for dominance over who gets to mate with the female swordtail fish.


The best way to balance the ratio is to have a single male for each 4-5 female swordtail.

This way, your male fish will have plenty of females to mate with and won’t need to fight.

4. Poor Diet

Swordtail fish are strong eaters, and they need enough food to be around.

If you don’t provide them with the correct nutrients, will start to bite the aquarium plants, attack minnows or shrimps, and chase and bite each other.


From our experience, we recommend providing your Swordtails with a diet that is high in both proteins and fibers.

Almost any type of food will suffice for the Swordtail fish. They may be fed live foods or high-quality dry food.

These species require two to three feedings every day, so make sure you stick to a strict feeding schedule.

Also, don’t forget water cleanliness, it is important to clean any food residues from the tank as soon as possible.

5. Boredom

Swordtails need a lot of space and plants to live. They also need hiding places where they can go when they feel stressed.

If you don’t provide them with enough space or plants, they can become bored and start biting each other.


To keep your Swordtails from getting bored, you should provide them with plenty of plants and hiding places.

You can also add some rocks, caves, or driftwood to the tank. This will give your fish something to explore and keep them happy.

6. Bad Water Conditions

Temperatures, pH levels, and other factors in swordtails’ environments might all contribute to aggressive behavior.

Let’s say that, for example, your water quality isn’t suitable, or you’ve recently transferred them into a new aquarium with different temperatures and chemicals from their old home.

If that’s the case, swordtails may not be able to deal with the changes and grow violent.


Swordtails thrive in warm water with a temperature of 65-80 degrees Fahrenheit, pH levels of 7.0-8.4, and hard water with a GH level of 12-30.

So, when setting up a new aquarium, make sure the water meets these requirements.

You can use a water conditioner to make sure the pH and hardness levels are where they should be.

Some Additional Tips to Get Rid of Your Swordtails Aggressive Behavior?

Changing the Aquarium Décor

If your swordtails are still being aggressive after following all the steps above, then you might need to change up the aquarium décor.

Why is this important? Quite simply, it will give fish a new environment to explore and can make them less aggressive.

Also, this will destroy all of your tank’s established hierarchies, forcing your fish to begin again from the ground up.

This can be beneficial because it will give the weaker fish a chance to thrive and get the food that they need.

Add Some Plants

A violent attitude might be an indication that your swordfish tank isn’t appropriate for them.

So, you should put plenty of plants and boulders in their new home to ensure that they are calm.

If you don’t have the time to redecorate your aquarium, choose plants that are tall and bushy rather than short and leafy.

This because plants that are too small may be interpreted as hiding spots for food, which can lead to tension between your fish.

Separate The Aggressive Fish

If your Swordtail fish is acting agitated, you should isolate it from the rest of the fish for a week or two. This will give the other fish time to reorganize the tank and make the Swordtail less dominant.

After that, you can reintegrate the hostile fish into the tank once it has relaxed.

Keep Them in An Appropriate Group

Keeping your swordtail fish in groups of four individuals (one male to three females) is one of the most effective methods for keeping them quiet.

If you have only one swordtail, adding more will also address this issue.

Are Male Swordtails Aggressive?

Generally, swordtail males are not aggressive. However, if there are several males in one tank, they may start fighting over territory or mates.

Are Female Swordtails Aggressive?

Female swordtails are not aggressive. However, some cases, such as pregnancy and stress may drive them to act violently.

How Can You Tell If They Swordtails Fighting?

Chasing and nibbling on other fish are some signs that your swordtails might be fighting.

Other signs include

  • You may notice nipped or broken fins.
  • When bullied, weaker fish will usually hide in aquarium plants or ornaments and tend to be lonely a lot of the time.

If you spot any of the following activities taking place in your tank, be wary that it is because of bullying. As soon as feasible, identify and separate the aggressive fish from the tank.

Can Swordtail Fish Kill Each Other Or Other Fish?

Swordtail fish have been known to devour one another or smaller, less powerful species in the tank.

This is very rare to happen, still, there’s a chance that you’re keeping a dominant alpha male in your tank who is constantly bullying others.

The weaker one may be harassed or pursued by the stronger one until they are overwhelmed, causing them to get severely stressed.

Do Swordtails Eat Their Fry?

Swordtails will feed on their fry if they are not well-nourished. So, it is essential to look after the youngsters.

Swordtail fish, like most livebearers, do not have parental instincts and will sometimes confuse their fry for food.

Therefore, you must take safety measures to ensure the babies are safe until they get bigger.

To protect the fry from their parents, you can:

  1. Separate pregnant fish at spawning time.
  2. To provide secure hiding places, put live plants in the aquarium.
  3. Get a breeding box for each breed.
  4. Remove the adult fish after they have given birth, and keep the fry seperate until they are big enough to be distinguished from food.

Are Swordtails Fin Nippers?

Swordtails are not typically a nipping fish, but they may do it as a form of aggression during fighting or mating.

However, if your fish has damaged fins or tails, you must pay close attention to it since this might spread diseases.

What to Do With Bullied Swordtail Fish?

When bullied swordfish are displaying signs of injury or disease, it’s usually time to transfer them to a different tank.

This is especially important if your swordtail fish is acting aggressive and chases and nips other tank mates.

Final Words

Swordfish are not particularly aggressive and livebearers even less so. When the fish are not happy, you can only observe these kinds of hostile behaviors.

Overall, it is important to keep your Swordtails in a spacious environment. It is also essential that you provide them with enough food and plants, and make sure they have a good male-to-female ratio.

By following these steps, you can prevent your Swordtails from becoming aggressive and biting each other.

We hope this article has helped you understand more about why your fish might be behaving this way and what you can do to change the situation. Good luck!

If you have any questions or would like to share your own experiences with swordtail fish, please leave a comment below.

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