Fish & Aquarium

Why are my Neon Tetras Fighting?

by Nadine Oraby

Neon tetras are one of the most popular fish for aquarium enthusiasts. They are vibrant freshwater fish with a peaceful temperament. However, sometimes neon tetras 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 size aquarium but a large stock of fish can also trigger their aggressive behavior.

In this guide, we will explore why neon tetras fight. Let’s get started.

Neon Tetras Swimming Behavior

Neon Tetras have a unique way of swimming. They like swimming in schools but 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 problems. Neon tetras may lose temper and start to fight.

People often feel claustrophobic in tight shared spaces with little room for movement. The same is true for neon tetras. They may like swimming in schools, but they want personal space. Look up online guides on fish tank size to avoid over-stocking. For a 10-gallon fish tank, you should keep up to six neon tetra fish. You’ll find some active neon tetras, and these are the ones that create trouble. If their behavior remains aggressive after twenty-four hours, you should consult a professional about the behavior.

Tetras aren’t violent creatures that fight, but you should show concern if they are truly fighting. 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.

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.

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 it does not, then you need to figure out why.

Nipping at Fins

Neon tetra fish are fin nippers. Most fish will nip rival fish’s fins if they feel stressed or irritated, but it is normal behavior for neon tetras. You will not have to worry about this problem unless it becomes extreme. Neon tetras love to chase other fish without showing aggression or attacking them. They are very playful fish and can stress out beginners who have never had neon tetras.  

People often misunderstand fin nipping behavior. They quickly assume that neon tetras are trying to fight. A stressed neon tetra can also start nipping other fish’s fins. Moreover, 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.

This is completely normal; you don’t have to worry about it.

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.

Dominance: Some neon tetra may want to be the dominant one, or they are the dominant fish and want to express it. They will show the new neon tetra where they fall in the fish hierarchy. Sometimes the dominant neon tetra may want to pick on the new neon tetra.

Territorial: 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 fighting or playing?

You might get anxious if you notice neon tetras chase 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. Neon tetras love chasing other fish, and this is nothing to worry about. However, neon tetras may fight in a small aquarium. The best thing you can do is provide an aquarium that has enough space for free movement.

Are they 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.

Do Neon Tetras Bully Other Fish?

Neon tetras prefer swimming in their school and are comfortable with other fish in the tank. However, introducing new fish in the tank can trigger bullying. The new neon tetra may start to lose their color or stop swimming with the school. The bullying will stop once the new fish adjusts to its new mates.

Neon tetras don’t prefer swimming with larger fish because they bully or eat them. If this is happening, put your neon tetras into a separate aquarium. Fighting and attacking can also be a way of expressing aggression. 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.


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. Check the ammonia levels and make ensure that the conditions are stable. You can also check the temperature and water parameters to avoid possible triggers.

Frequently Asked Questions

Can tetras be aggressive?

Tetras are very peaceful fish, and people buy them because of their calm nature. But some conditions can make them highly aggressive toward other tank mates.

Can 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, 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 prefer a school with members of their species. They are best adapted to swimming with their species and form a happy, non-aggressive school. Small fish feel safer in groups because it is easier to confuse predators.

Photo of author

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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