Are Swordtail Fish Aggressive? All You Need To Know

Lauren Kiekbusch
Are Swordtail Fish Aggressive

Exclusion of intersexual competitors (direct) or defending resources required to attract mates can all be part of the competition for mating opportunities (indirect). Male swordtails compete head-to-head. Furthermore, they protect a home range in wild populations.

This study aimed to see if home range defense is a type of food resource defense, and if so, what effects it might have. When describing the nature of their swordtail fish, many aquarists find themselves at a fork in the road.

There have been reports of this tropical fish species becoming extremely forceful and domineering on several occasions. They will sometimes push everyone around and take over everything, including the sink.

In this article, we will discuss the aggressiveness in the swordtail fish and the causes.

Also worth reading;

  1. Do Swordtail Fish Sleep?- You Might Be Interested To Know
  2. Why Do Swordtail Fish Eat Their Fry? ( All You Need to Know )
  3. Swordtail Fish Fry Care – How to Care for Baby Swordtails?

Are Swordtail Fish Aggressive?

Generally, swordtail fish are very peaceful and will remain in that status as long as they have adequate habitat. These tropical fish species are very friendly so they can survive in a wide range of conditions.

As a result, the swordtail fish are the best and ideal fish for a beginner. However, several factors can cause your swordtail fish to become hostile.

In most circumstances, you’ll notice that male fish are more aggressive toward their male counterparts.

It holds female swordtails as well. It’s a matter of territory. A modest adjustment in water perimeters might also result in dominance and violence in some cases. Again there are different reasons why these fish species can show aggressiveness at one time when they wake up. These factors are discussed in the article below.

Aggressive Behavior Between Swordtails

How a fish behaves can help you determine if it’s aggressive or not. You may or may not be in the know. But how does a ferocious swordtail behave?

In the tank, a gang of bullies’ swordtails sees themselves as gods. They desire to be revered.

Other innocent and shy-looking contemporaries will be pursued in the wrong direction. Like lions in the forest, these bullies are known for their cruelty.

These bullies are not always born like that. Sometimes you may sleep when these swordfish are very peaceful, only to wake up and find that they are bullying each other. This bullying, you may think, is caused by the big swordtail only to find that the small fish is the problem.

It is advisable to find the bully among the fish and separate it from the others in such a case. This action of separating bullies from the other fish for some time makes the bully calm down.

After calming down, taking the fish back to the original tank where the others are located is good. Again, it is also advisable to take out the bullied fish from the original tank and leave the females and the bullies.

Bullying produces stress in other fish, making the bullied fish more susceptible to tropical fish diseases due to the pressure. Bullying can also cause injuries to the bullied fish’s fins, interfering with their daily tasks like swimming and breathing.

Causes Of Aggression In Swordtail Fish

Different factors cause aggression in a swordtail fish. These include:

  • Inadequate male-to-female ratio
  • Overcrowding in the tank
  • Pregnancy
  • Small swimming space

1. Overcrowding In The Tank

Different fish species tend to live in harmony and peace in natural settings such as rivers, lakes, and oceans because they have enough space. On the other hand, they do not need to scramble for them to obtain the fundamental supplies for a healthy lifestyle.

The amount of room available in an aquarium tank is minimal. Due to the overcrowding in the tank, stronger swordtails will establish their territorial limits.

As a result, every fish that enters their borders is pursued and fought to the death. Second, the swordtails stay stressed and aggressive in a crowded tank.

To avoid overcrowding, you can get a larger tank or keep a recommended number of fish in the existing space. You should not put too much in the tank to make the most of the available space in the tank.

Swordtails are superb swimmers, so keep that in mind. Always double-check that the available area can comfortably fit each fish.

Are Swordtail Fish Aggressive

2. Male-To-Female Ratio

It is critical to maintain a proper male-to-female ratio. With more males in the tank, they are likely to battle each other. Female swordtails have the same problem.

On the other hand, male swordtails usually follow female swordtails to mate when they achieve sexual maturity. Scrambling occurs during this period, and the stronger male will take control and exhibit hostile behavior toward another male.

3. Small Swimming Space

Swordtails, as previously said, are excellent swimmers. They may be as few as you think, but your tank may not fit them. The fish, on the other hand, may require hiding places.

Live plants provide them with protection. The primary goal is keeping an aquarium closely resembling a natural habitat. Your swordtail will survive as a result of this.

4. Pregnancy

Swordtails that are pregnant are often agitated. As a result, their violent behavior increases. Second, pregnant swordtails are constantly lonely, usually at the bottom of the aquarium, due to the increased burden. Their movements are restricted to specific locations. They will not want to be disturbed because of this aspect.

Any fish that tries to get in the path of the pregnant fish is hunted down and fought. Because of their vulnerable state, the pregnant swordtail fish is kept in a separate tank until the livebearers are born.

It will not only shield her from stress and disruption but also allow you to observe her throughout the pregnancy, giving you plenty of time to preserve the livebearer.

5. Limited Swimming Space

Swordtails, as previously said, are excellent swimmers. They may be as few as you think, but your tank may not fit them. The fish, on the other hand, may require hiding places.

Live plants provide them with protection. Your primary goal is keeping an aquarium that resembles a natural habitat. With that kind of habitat, the swordfish will live a stress-free life.

What’s The Deal With Male Swordfish Fighting?

Swordfish males compete for control of their territory. Like any other animal, they have a strong desire to keep certain areas of the aquarium to themselves. As a result, they will go to any length to keep these precise locations. Second, the alpha male may compete for mates with other sub-males.

The sub-male swordtails’ nature is to remain in a particular corner, anxious and unable to flee. You might mistake them for females while they’re younger and don’t have a longer sword-like tail.

Is It Possible For Swordtails To Kill Each Other?

Yes. Swordtail fish have been known to murder each other in the past. An alpha male who decides to assert control over other sub-males can be a genuine annoyance.

He will always pursue the other sub-male, even if it is in the wrong direction. As a result, other sub-males will continue to be stressed, and disease-prone, and the sub-male often die.

Second, it is customary in fights for the alpha male to continue chewing the sub-tail. The sub-male typically suffers significant injuries as a result of this and eventually dies.


Swordtail battles are a common problem that many aquarists worldwide have noticed. It’s a sign that the tank is home to aggressive swordtails. However, if you care about your pets, don’t wait for them to perish at the hands of alpha males.

To reduce the rates of hostility among the fish species you keep in your aquarium, first figure out what is causing the aggression. After that, take the appropriate steps to resolve the issue.

More about Swordtail Fish; You should watch this video below;

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