Why are my Neon Tetras Fighting?

Neon tetras are one of the most popular fish for aquarium enthusiasts. They are vibrant freshwater fish with a peaceful temperament. However, neon tetras sometimes can show aggression and fight other fish in their school.

Neon Tetras show aggression in different circumstances, such as while mating or feeding. Having a small-sized aquarium for a large stock of fish can also trigger their aggressive behavior.

In this guide, we will explore why neon tetras fight and how you can prevent it. Let’s get started.

Why Neon Tetras Fight – Find Out!

Neon Tetras Swimming Behavior

Neon Tetras have a unique way of swimming. They like swimming in schools but need enough space to swim without bumping into each other. Even though they’re pretty tiny, keeping 7-8 neon tetras in a small tank will make them aggressive. They prefer swimming in a distinctive pattern, and bumping with other fish can cause them to lose their temper and start to fight.

Just like some people feel claustrophobic in tight shared spaces with little room for movement, neon tetras feel the same. They may like swimming in schools, but they want personal space. The best way to prevent this is to avoid overstocking. For a 10-gallon fish tank, you should keep up to six neon tetra fish.

Overstocking and Rival Fish

If you spot active neon tetras, they may be the ones creating trouble. If you’ve recently changed their tank or brought new neon tetras home, allow them some time to adjust to their new environment. If they stay aggressive after twenty-four hours, consult a professional.

Tetras aren’t violent creatures, but it should be concerning if you find them fighting often. They usually fight if there isn’t enough space to swim. Focus on the tank size and make sure you don’t stock rival fish that are not compatible with neons. This triggers aggressive and violent behavior among your fish.

Wrong Water Temperature

Additionally, maintain the water and temperature at optimal levels to avoid irritating neon tetras. Habitat change can affect their behavior and make them more aggressive. They express their distress by fighting.

The ideal water temperature for neon tetras is typically between 72°F to 76°F (22°C to 24°C). Maintaining the water temperature within this range helps keep these tropical fish healthy and active in an aquarium setting.

Stress or Disease

When there is a sudden change in a neon tetra’s behavior, it could also indicate stress or disease. If neon tetras change their swimming style, you should monitor the parameters of the water. Something could be stressing or initiating them. Sick neon tetras may also swim irregularly and bump into other fish.

You also need to be cautious if the neon tetras are not swimming around the aquarium. They might be feeling threatened by another fish. Try to separate the problematic fish and see if their swimming style returns to normal. If not, you need to figure out why.

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Nipping at Fins

Neon tetra fish are known for occasionally nipping at the fins of other fish, but it’s usually not a big problem unless it gets severe. They tend to playfully chase other fish, which is a part of their natural behavior. This behavior may surprise beginners, so it’s important to be prepared for it and ensure the right tank conditions and compatible tank mates to prevent stress.

People often misunderstand fin-nipping behavior. They quickly assume that neon tetras are fighting. A stressed neon tetra can also start nipping other fish’s fins. Older fish can go around chasing and fin-nipping the new fish in the tank. Tetras also fin-

People often misunderstand fin-nipping behavior. They quickly assume that neon tetras are fighting. A stressed neon tetra can also start nipping other fish’s fins. Older fish can go around chasing and fin-nipping the new fish in the tank. Tetras also fin-nip to protect their territory from any danger or threat.

Here are some reasons your neon tetras might be nipping the fins:

Introduction of New Fish

When you introduce a new fish to the tank, the older neon tetras will nip at its fins. This is because the new fish is a stranger to them. This could last a while until they start to get along in the same aquarium.


Occasionally, neon tetras may exhibit dominant behavior, especially when new members are introduced to their group. In such cases, the dominant individuals may establish their position in the fish hierarchy and may occasionally pick on the newcomers. This behavior is a natural part of their social interactions within the group.


Some neon tetras want to establish territory and may nip at the new fish’s fins.

Protection: It could be a way of protection and defense against any threats.

Are They Really Fighting?

Fighting or Playing?

You might get anxious if you notice neon tetras chasing each other in the aquarium. Beginners may assume that they are fighting. But what if they are just playing?

Neon tetras are playful and tricky creatures. Many people can’t differentiate between their fighting and playing behavior. They love chasing other fish, and this is nothing to worry about. But it is important to be sure they’re not fighting. If they have ample space to swim around without being territorial, it’s highly likely they’re just playing. The best thing you can do is provide an aquarium that has enough space for free movement and ensure optimal water temperature to keep them calm and happy.

Fighting or Mating?

When some fish are practicing their mating rituals, it may look like they are fighting. When it is mating season, the male neon tetras will fight to win the female.

Here’s a way to determine if your neon tetras are mating:

You can put a male and female neon tetra in a different aquarium with the right conditions for mating. Notice if the male tetra starts to swim in a square pattern and behaves oddly. It’s a clear indication of mating, and the male will fertilize eggs very soon.

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Do Neon Tetras Bully Other Fish?

Neon tetras typically thrive when they swim together in a school and are generally peaceful with other fish in the tank. However, when introducing new fish to the tank, it can sometimes trigger bullying behavior. The newcomers may experience some stress, which could cause them to lose their vibrant color or swim separately from the school initially. This bullying behavior usually subsides as the new fish adapt to their new tankmates and surroundings.

Neon tetras avoid swimming with bigger fish because they can get bullied or eaten. If this happens, move them to a separate tank. Sometimes, fish fight or attack to show who’s boss in the tank. Neon tetras are excellent at detecting the slightest change in their habitat. If you’ve changed their habitat conditions, it could make them aggressive. They may refuse to eat or even start to bully other fish.

Frequently Asked Questions

Are tetras aggressive by nature?

Tetras are typically peaceful fish, but certain conditions (as mentioned in the article above) can make them aggressive towards other fish in the tank.

Do neon tetras die easily?

Neon tetras can live up to fifteen years, but they can die easily with the slightest change in the aquarium environment. If there are any sudden changes in water chemistry, the fish begin experiencing stress and anxiety and develop low immunity. It makes them susceptible to catching all kinds of diseases and illnesses.

Are four neon tetras enough?

Keep your neon tetras in schools of 4-6. They are active, schooling fish that swim horizontally. Use rocks, plants, and driftwood to provide entertainment. You should also provide optimal water conditions and keep the tank clean.

Are neon tetras more active at night?

Most aquarium fish are diurnal, meaning they move about during the day and rest at night. However, some species are nocturnal and prowl at night, spending daylight hours sleeping in a cave or crevice. While the Neons are huddled on the bottom at night, the catfish are cruising around looking for an easy meal.

Can you mix neon tetras with other fish?

Mixing neon tetras is not a good idea and may cause them stress. Tetras are happiest when they are in a school of their own kind, swimming together without aggression. Being in a group provides them with safety in numbers, making it harder for predators to single them out.


Neon tetras have a peaceful temperament, but they can fight under some conditions. Consider buying a large aquarium to keep the neon tetras from fighting. They need a spacious tank to practice their unique swimming style. Regularly check and maintain stable water conditions, including ammonia levels, temperature, and other water parameters, to avoid triggering any aggression among them.

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Nadine Oraby

My name is Nadine; I am a passionate writer and a pet lover. People usually call me by the nickname “Joy” because they think that I am a positive and joyful person who is a child at heart. My love for animals triggered me to create this blog. Articles are written by vets, pet experts, and me. Thanks for visiting. Your friend, Nadine!

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