Are Neon Tetras Aggressive? (And Signs To Look For)

Last Updated on 2023-05-24

When you are populating an aquarium, it is important to do your research and make sure the fish you choose are all compatible. Some fish are more aggressive than others, which could cause issues, and it is something worth investigating before bringing a new species into your tank. How about Neon Tetras? Are they aggressive?

While Neon Tetras can be aggressive, the species isn’t known for being aggressive. Let’s have a look at when aggression can be expected and what to do about it.

Are Neon Tetras Aggressive?

Neon Tetras are very popular fish in aquariums worldwide, and they are not known for being aggressive. In fact, they tend to be very peaceful and easy to care for, and it makes them easy to pair with suitable tank mates. That said, Neon Tetras can show aggressive behavior in specific situations, and while rare, it happens.

Neon Tetras should preferably be kept in groups of at least six, and even though they often get along just fine most of the time, there can be issues when the fish is mating or feeding. It is not known as an aggressive fish, no, but aggression can still surge. 

Do Neon Tetras Fight Each Other?

It is not common for Neon Tetras to fight each other or to go after others within their own group. Most aggressiveness happens in response to a poor choice of tank mates or another fish interrupting a Neon Tetra while feeding or mating. On occasion, Neon Tetras may get into disputes with other Neon Tetras. 

What Causes Aggression In Neon Tetras?

As pointed out, this is a fish that isn’t known for aggressive behaviors, and that is much more likely to act peacefully in the tank, but if you have issues with Neon Tetras fighting, the key is to figure out what is causing the fights in order to stop it from happening.

The fact that these fish rarely fight makes it a serious cause for concern when they are fighting, as it goes against their nature, and there might be something you can do to optimize their living conditions and stop the fighting from becoming recurring.

Resource Guarding

If you start noticing fights breaking out around the time you feed your aquarium fish, or when the Neon Tetras are close to something edible in the tank, then you might be dealing with a form of resource guarding! This does not tend to be a unique issue, and resource guarding is usually caused by something else.

Yes, some fish do become aggressive when another species approaches their food, but Neon Tetras are peaceful and friendly for the most part. Lack of space, which we will get to in a moment, could contribute to the fish feeling a need to guard their food supply.

Lack of Space

When there isn’t enough space for Neon Tetras to swim around, they tend to get frustrated and irritated. Irritated fish are more likely to lash out and start (or finish) fights with other fish, and this is the first thing you should consider if you are noticing fights in your tank.

Have a look at your fish tank to see if your Neon Tetras are given the space they need to swim, play, eat, and generally thrive. If the tank is cramped, consider investing in a new tank or remove some plants and/or other tank habitats. A full tank looks pretty, but Neon Tetras need their space.

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Aggression in Neon Tetras is considered an abnormal behavior for the species, but it could occur during mating. It is not recommended to breed Neon Tetras in the community tank for this reason, but also because the eggs are likely to get eaten by other species.

Make sure you move your Neon Tetras to a separate tank for mating to avoid instants of aggression. You don’t want to put your Neon Tetras in a situation where they would have to be aggressive to protect themselves and their spawn, and it is always better to set them up for success by separating them from the main tank.

Water Conditions

If you are sure the tank size is right, your Neon Tetras have space to swim, and everything seems fine, then it is time to start considering the water conditions. It is not the most common reason for fighting, but inadequate water conditions could make the Neon Tetra uncomfortable, which could easily lead to irritability. 

On the plus side, Neon Tetras are not too picky with temperature, water hardness, and such, but it is still something worth keeping an eye on. The ideal water temperature for Neon Tetras is 70°F to 81° F. They prefer dimmed lighting, soft water, a pH above 6.0 and below 7.0, and a tank size of at least 10 gallons. 


Another extremely common reason Neon Tetras show aggression is food. Since they are school fish, the competition for food is usually high. Their aggression will increase if there are other fish in the tank with the school. It is hard to make sure all of the Neon Tetra get enough food.

Aggressive Tank Mates

One aggressive tank mate can lead to other fish becoming aggressive. If your Neon Tetra is in a tank with other fish, it is possible that other fish are being aggressive towards the Neon Tetra. This will cause the fish to become extremely stressed and eventually become aggressive as well.

(Find out the best tank mates for Neon Tetras.)


When your Neon Tetra is stressed, they are highly likely to show aggression. There are multiple reasons that your fish can be stressed. First, they can be unhappy with their water conditions. The temperature of the water is important because they are tropical fish. 

Neon Tetra can also become stressed if their tank is too small and they are crowded. They can also become stressed if there aren’t enough decorations in the tank for them to hide in. You will be able to tell if your fish is stressed by the way they behave.

In addition to acting aggressive, your Neon Tetra might show stress in other ways. They could have a loss of appetite, start swimming differently, try to hide more often, and make sudden, jerking motions. They might also stay close to the top of the surface, have changes in their appearance and lose color.

If you feel like your fish is stressed, you will want to address the situation immediately. If not dealt with, your fish can experience damage to their scales, a weakened immune system, and issues with their mucus. All of these can be life-threatening.

Illness or Injury

If your Neon Tetra has an illness or injury, they can also show some aggressive behavior. Even the slightest injury or sickness can cause your Neon Tetras to be in pain and uncomfortable. There are several different diseases a Neon Tetra can catch, including ich, growths on their mouth, and Neon Tetras disease.


Neon Tetras are extremely playful fish. It is easy to confuse the way they play with aggression. The fish are likely to play with each other by chasing each other and jumping high in their tank. You should be able to easily tell the difference between fighting and playing.

What Are The Signs Of Aggression Occurring?

Neon Tetras are very playful fish, and it is normal for them to be swimming back and forth, chasing each other around, and acting somewhat erratically. This is not a cause for concern, but it can take a while for the untrained eye to recognize when it is regular play and when your Neon Tetras are fighting. Here are a few signs of aggression:


Pay attention to the way your Neon Tetras swim. If one appears to be swimming separately from the school, there is a chance it might be bullied by the other Tetras. These fish usually get along, but when a new Neon Tetra is introduced, the other will sometimes start bullying it.

When a Neon Tetra is severely bullied, it stops swimming with the rest. You may also notice a change in color and how the bullied fish becomes less colorful with time. A situation like this needs your interference, as the affected Neon Tetra might otherwise die.

Fin Nipping

A potential issue is that Neon Tetras are prone to nip at the fins of other fish, both other Neon Tetras and other species. Fish with longer fins tend to be at a bigger risk of getting nipped. If your Neon Tetras are nipping at the fins of other fish in the tank, it is a sign of aggression that is usually provoked by stress. 

How Can You Stop Neon Tetras Acting Aggressive?

Solving the issue of a Neon Tetra’s aggressiveness requires two simple steps. First, determine why they are fighting or acting aggressively, and take the required action to eliminate the problem. The solution will be different depending on the cause.

More Space

If your Neon Tetras are showing aggression due to lack of space, you can prevent this two ways. First, you can reduce the population in the tank. Move some of the fish to another tank to create more room. If you don’t want to add another tank or separate the fish, you can upgrade to a larger tank.

To properly accommodate a school of Neon Tetra, it is recommended that the tank holds two gallons of water for each fish in the tank. If your school has ten Neon Tetras, the tank should be able to hold twenty gallons of water.

In addition to giving your Neon Tetras more space, you should also give them more places to hide. You can do this by adding decorations, structures, and live plants to the tank. This will allow weaker fish to quickly find a place to get away from an aggressive situation.


If you want to prevent aggression due to mating, it is possible. Neon Tetras aren’t likely to breed unless there are perfect breeding conditions. They will usually only breed in soft water conditions and an acidic pH balance.

Keep their water in conditions that aren’t likely to allow them to breed. As long as the conditions aren’t perfect, it is not likely for the Neon Tetra to try to mate. If you want to be completely sure your Neon Tetra won’t breed, you can have one sex or keep the two in separate tanks. 


If you notice your fish becoming aggressive over food, you should start monitoring them when they eat. This will help you understand if you need to feed your fish more or separate smaller fish from larger fish. It is recommended to feed a few flakes of food per fish.

Even if you are feeding your fish a sufficient amount, it doesn’t mean that every fish can easily access the food. After watching them feed a few times, you will be able to tell which fish are having to fight and get aggressive over food. You can separate these fish, and the fighting should stop.

Tank Mates

If you think your Neon Tetras are becoming aggressive because there are other aggressive fish in the tank, you should remove the aggressive fish. This will reduce the stress level of the Neon Tetra and calm them down, getting rid of the aggressive behavior.


One of the best ways to prevent aggression caused by stress is to prevent and reduce the amount of stress the Neon Tetras feel. The first thing you will need to do is make sure you have the temperature of their water set perfectly. To be happy, they need the water to be between 72- and 78-degrees Fahrenheit.

You will also need to keep their tank clean to reduce stress. You can do this by cycling about twenty-five percent of their water to clean it. You want to gradually change their whole tank of water to prevent even more stress. 

Illness or Injury

If you suspect that your fish is becoming aggressive because they are sick, you will want to move them immediately to a quarantine tank. If you can’t figure out why they are sick, you should contact a vet as soon as possible. If you do know why they are sick, use the proper medication to treat. When they aren’t sick anymore, they can be reintroduced to the main tank.

Help from a Specialist

Persistent aggressiveness might require help from a specialist, and especially if you have already tried everything to eliminate the behavior. As mentioned, it is not normal for the species to fight and show aggressiveness and could potentially be a medical issue or an abnormal behavioral problem.

What’s the Difference Between Aggression and Playing?

Neon Tetras love to play with each other. They will do so by chasing each other around the tank, jumping high in the tank. It will usually be easy to tell the difference between playing behavior and fighting behavior.

It is completely normal for your fish to swim around after each other. This is how they interact and have fun together. In some cases, one fish might be chasing another to get them out of their territory. While this isn’t playing, it isn’t exactly aggression either. They don’t intend to hurt the other fish; they just want to be alone.

When the fish are actually fighting, it is likely that one fish will feel threatened and start to cower into a corner. Instead of fighting back with the aggressor, this fish is trying to protect itself from harm and will isolate itself. This is a sign that there is some aggression coming from the other fish, and they are not playing.


Neon Tetras are not aggressive, but they can show aggressive behavior if stressed or uncomfortable. Stress could be provoked by a lack of space in the tank, the wrong tank mates, poor water conditions, or bullying, and it is something you need to deal with if it happens.

The fact that Neon Tetras are not considered aggressive, aggressiveness becomes a sign that something isn’t right in the aquarium. Pay attention to your Neon Tetras and how they behave, and if you notice aggression, start by determining the cause of the fights.

In most cases, aggression in Neon Tetras is a direct result of something being wrong in the tank, and it is an urgent issue when these peaceful fish start acting up.


Are Neon Tetras Fin Nippers?

Yes, Neon Tetras are known for being fin nippers. However, the behavior is tied to stress, and a Neon Tetra that nips at the fins of other fish is likely stressed or uncomfortable in the tank.

Will Neon Tetras Kill Each Other?

It is not unusual for Neon Tetras to bully each other or pick at each other, but they are not likely to kill other Neon Tetras unless one is sick or already injured. Provided you have a tank with hiding spots and places for Neon Tetras to take cover, they are unlikely to kill each other.

Do Neon Tetras Die Easily?

When the tank conditions are right – Neon Tetras can live for up to (an impressive) ten years! However, if there is a sudden or drastic change, such as a water temperature change, Neon Tetras do die easily.

How Many Neon Tetras Should Be Kept Together?

How many Neon Tetras you can keep in a tank depends on the size of a tank. The recommended minimum is 6 Neon Tetras, but they are usually happier if you keep at least 10 in a 10-gallon tank. A 20-gallon tank is preferred if you wish to keep more than 10.

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