Are Swordtails Aggressive?

Swordtail fish are a wonderful addition to any aquarium. They’re simple to care for and don’t need much effort. These fish prefer to be in a group. However, groupings can be dangerous since certain fish may become hostile. You may wonder; are Swordtails aggressive?

Swordtails aren’t naturally aggressive. However, some situations can cause these fish to become hostile. If there are a lot of males, this could lead to rivalry when they reach maturity. Additionally, pregnant fish may exhibit aggression.

In this article, we’ll explore what causes Swordtails to become hostile and how you can resolve the issue.

Are Swordtails Aggressive?

Swordtails are calm and non-aggressive fish by nature. When they reach sexual maturity, however, they, like most animals, can become hostile.

It’s best to keep them in a group of five or six fishes, with only one male among them. If you want to keep your Swordtails among other types of fish, catfish are a good choice. They aren’t only friendly, but they also have similar water needs.

Group of Swordtails on Gravel

What Can Cause Swordtail Fish to Be Hostile?

Swordfish don’t become aggressive without being provoked. Because they’re naturally peaceful, there are only a few explanations for why they might act angrily.

Crowded Tank

Tanks come in a variety of shapes and sizes. If there’s a lack of space, fish may get hostile. Swordtails prefer to have their area large and roomy.

Stronger Swordtails will set their territorial boundaries if the tank is packed. As a result, every fish that passes its territory tends to be in danger.

You can get a bigger tank or keep the minimum number of fish in the given space to prevent crowding. A Swordtail requires at least 15 gallons of water. For each added fish, five or six gallons of water are required to keep them satisfied.

Swordtails are energetic and require a large amount of swimming room. So, avoid overcrowding the tank with decorative items.

Pregnant Female Swordtail

Pregnant Swordtail fish, like other animals, will be aggressive. Between the ages of four and five, females reach sexual maturity. Females can deliver a range from 1 million to 29 million eggs, which differs based on size.

Pregnant fish are more agitated, and their movements are restricted to specific areas. They will not want to be disturbed because of this issue.

Swordtail fish normally stay pregnant for about 28 days. It’s best to isolate the pregnant Swordtail fish during this time until she gives birth. It will be beneficial to the fish because you will be able to tailor the tank to meet their demands.

Healthy food, a water temperature of 80° F, and a pH of 7-8 are required for pregnant Swordtail fish to be healthy. Separating your pregnant fish will not only benefit her, but it will also protect the other fish.

Male-To-Female Ratio

Keeping a good male-to-female balance is necessary, as previously stated. The likelihood of the fish attacking each other increases as the number of males in the tank increases. Therefore, just one male should be kept in a group of five to six Swordtail fish.

Female Swordtails may be violent as well during that age. However, male fish will pursue female fish to reproduce when they reach sexual maturity. So, males tend to be more hostile. The dominant male will take command and display aggression toward the weaker male.

Signs Of Hostility In Swordtail Fish

Keep a lookout for those actions if you feel your fish is becoming hostile. These are indicators of aggressive behavior.


Other fish will be chased away from the Swordtail fish’s domain. When you add a new fish to the tank, you’ll notice this behavior the most. The current fish will attack the new fish. Most Swordtail species, including platies, display these behavioral problems.

While gradually adding new fish may appear to be a smart idea, it isn’t the best way. It’s ideal to put all of your new fish in one go into your water tank.

Fin Nipping

If your fish has been harming the fins or tails of other fish, this is known as fin nipping. Fish do this all the time, regardless of how big or small the other fish are. Fish can also perform this behavior on themselves.

Fin pinching can put the life of the fish in jeopardy. When fish are harassed, they become anxious and more prone to sickness. If there isn’t enough food, this behavior can occur.

If your Swordtail begins to exhibit this behavior, you should separate it. Reintroduce the fish to the tank after a week, and keep a close eye on its behavior. If isolating the fish to the tank doesn’t stop the bad habit, it must be removed and kept in a separate tank.

How To Control Aggressive Swordtail Fish?

There are several things that you can do to maintain peace within your tank:

Isolate The Aggressive Fish

For the time being, the violent Swordtail should be kept in a separate aquarium. This will provide the fish with some time to reduce the negative behaviors.

Isolate the Swordtail for at least a week or two. The longer the agitated Swordtail fish is isolated from the rest of the group, the better. This will allow the other fish to reorganize the tank’s structure and grow more dominant.

You can reintroduce the hostile fish to the tank once it has calmed.

Feed Them Appropriately

Swordtail fish can become hostile if they don’t get sufficient food. Therefore, make sure they have food at all times.

It’s advised that you offer your Swordtails nutrients that are high in both proteins and fibers. Swordtail fish will eat almost any type of food. You can feed them live foods or high-quality dry food.

Swordtails require two to three feedings each day. To maintain water cleanliness, clean any food residues from the tank as soon as possible.

Rearrange Your Aquarium

Modifying your aquarium’s scenery can make a big difference. Because Swordtails can be territorial, changing the terrain can prevent territorial behavior. You should do that specifically If you intend to add more fish. In addition, ensure that your tank has enough hiding spots.

Some Swordtail fish prefer to hide in places where they can’t be seen. This will not only reduce stress for the fish, but it will also allow other fish to roam freely.

Hideouts will also enable hostile fish to establish a domain, leaving the other fish safe. Make sure your tank isn’t crowded. If an agitated fish feels cramped, it may act out negatively.

Wrap Up

Swordtail fish are generally peaceful, however, they can be aggressive at times. This could be due to a variety of reasons. These reasons include the presence of multiple males in the same tank and pregnant fish.

If you notice a fish behaving inappropriately, separate it from the rest of the tank for a week or so. Then reintroduce it to the tank. Now, you’ll have a happy aquarium.