Why Are My Neon Tetras Fighting?

If you’ve found this post you’re probably starting to pull your hair out and asking yourself “Why are my neon tetras fighting?” There are many reasons that could be behind your neon tetras’ aggressive behavior such as stress, illness, hunger and as with many animals, mating can be a source of aggression too!

The purpose of this post is to help you identify the possible reasons that your neon tetras are fighting and what you can do to about it.


Male Tetras will fight over the available female Tetras. If there is more males than females in your fish tank, this may become a problem. If you notice your Tetras getting aggressive and swimming in a square pattern, then mating will soon begin.

The solution to this is to ensure you have more female Tetras, as compared to male Tetras as this will reduce the likelihood of your males fighting over the female Tetras.

It is also not healthy for your fish and may also lead to thriving difficulty.

Newly Introduced Fish

Neon Tetras may sometimes behave poorly when you introduce a new fish to the tank. This is because they are protecting their territory. You may find your Tetra chasing after other fishes and nipping at their fins.

Observe your fish over a short period of time and see if the fin nipping behavior dies down. If it continues, it may be a good idea to transfer the aggressive fish or the fish being bullied into a separate tank.

Space is Limited

If you place a lot of fish in a limited space, this can trigger fighting in your fish tank. Tetras will start chasing each other so they can have space on their own. Placing decorations and various objects inside the tank may not be ideal, particularly if you have a small tank size.

The territory is also important to Neon Tetras, and they will act aggressively if other Neons are trying to cross their territories.

The key is in getting a bigger-sized aquarium that will be compatible with the number of Neons you have. Neon Tetras may be tiny, but they will benefit more with a bigger tank to freely move around and live peacefully with other Tetras.

Consider the decorations, plants, and other items you need to place inside the tank plus the number of Tetras you are planning to have, and then decide which tank size is right for them.

Not enough food

Hunger can make Tetras turn against each other. When there is not enough food for every fish in the tank, they will compete for it and even become aggressive to other fish. They will try to get their fill and will fight off those who will block them from having it.

If you are also incorrectly feeding them and there is a long interval between feeding times, this may also cause your Tetras to become too hungry for the next meal.

Although they can eat algae and insect larvae, this may not be possible in a home fish tank, and you need to provide the required food at the right time.

When they are in distress

Neons may also feel stress, and the water conditions can bring it about, as well as, change in their environment.

Some signs of stress in Neons include strange swimming patterns, no interest during feeding time, bullying other fishes, and staying at the tank’s surface.

Water conditions can bring a lot of stress to your Tetra. Sometimes, the cause is high ammonia, and nitrate levels, poor oxygen, the temperature is not ideal, or the pH level may be too high or too low. 

Improper feeding and change in their diet can also be the culprit.

Another factor is stress in their environment. If their tank is located where there are loud, banging noises and where people come and go, while frequently tapping at the tank is a sure-fire way to cause stress to your Tetras and lead to aggression from them.

They may not be in the best of health

Neons are generally peaceful, they want to be with their school, swimming away the time.

However, when they have contracted a disease, their behavior changes. You can find Neons in hiding, or chasing off other fish and fighting with them.

Observe what is causing their stress and why they are getting aggressive. Some signs of disease that you need to be aware of include

  • Fading color that usually starts at the fins until it consumes the Tetra. The previous eye-catching color is no longer bright but slowly dulls away.

  • Irregular swimming pattern and can even bump at other Tetras.

  • Red spots on their fins you can notice. Improper water conditions usually caused this.

  • White spots not just on the fins but on the entire body. These changes in them are obvious.

(Fore more help on keeping neon tetras check out our other article – How To Care For Neon Tetras)

How to stop your Neon Tetras from Fighting?

Get the Appropriate Tank Size

A pleasant living condition for Neons will be a tank where they can move around, they can stay in various corners with no other fish bugging them, or they are free to go up and down the tank without bumping with the other fish.

It is also ideal to provide some decorations where your Neons can hide and swim around but make sure that you are not overdoing it. Getting too many of the decorations, stones, even plants may no longer work if you are also planning to have a multitude of fish in your aquarium.

Always check the Water Condition

Certain parameters where your Neons will thrive are slightly acidic and soft water. The temperature should be between 72 to 76 degrees Fahrenheit, ammonia and nitrite at 0ppm, Nitrate at less than 20ppm, pH must be between 6 to 7, GH or General Hardness at less than 10 dGH, while the total Alkalinity between 1 to 2 dKH.

Filtration is also crucial in the fish tank since this will remove the excess such as decays, food, floating particles, chemicals, and other waste products. Choose one that can filter your tank without difficulty and should be compatible with the size of your tank.

Correct Ratio of Males to Females

You need to remember when you place more males in the tank, fighting often ensues, especially if there are not enough females around. You can place more females instead of male Tetras to lessen bullying, fighting, and aggressiveness. A good suggestion is to have at least two females for every one male making the ratio 2:1.

Plants and Decorations

A vast space where your Tetras can swim is vital, but having an atmosphere that copies their environment in the wild is also important.

Providing a setting with lots of plants and decors will be beneficial to the well-being and comfort of your Tetras. Having such can give them some hiding spots, exclusive areas where they can dart and hideaway. Plants can also remove nitrates from the water.

Some plants that you can use include Brazilian Pennywort, Ludwigia Repens, Cabomba, or Vallisneria.

Other options such as Frogbit, Dwarf Water Lettuce may also be useful.

Brazilian Pennywort
Brazilian Pennywort can be a usefuly plant to have in your aquarium

Feed them quality foods

Flake food that is high quality can be your choice, as well as, sinking micro-pellets. Food chips, wafers are also good. Offer frozen bloodworms, brine, shrimps, fruit flies, micro worms, and even mosquito larvae.

Since Neons are highly energetic fish, they need their daily feeding, one in the morning and then at night time. However, remember not to overfeed them, all food should be consumed within a maximum of 5-minutes, otherwise, leftover foods may lead to decay and contaminate your fish tank.

Make sure you remove leftovers after every meal.

Separate the fish with aggressive behavior

You may do this if you have already exhausted the other options and your Neon Tetras are still fighting with one another

You need to observe which Neon(s) are doing the chasing, nipping, and fin biting. This may be hard to figure out, but with keen observation, this may work.

You can isolate the bullies in a separate tank and then re-introduce them later on. Again, you need to keenly observe if there are any changes in their behavior at all.

You may also separate the weaker or the bullied fish. If the bully is zoning in on one or two fishes and you’re noticing their fins being nipped, you must transfer the weaker fish until they become healthier and tougher for reintroduction to the fish tank.

Why Are My Neon Tetras Fighting - Conclusion

Neon Tetras are generally a peaceful species of fish well suited form community tanks. If your neon tetras are exhibiting aggressive behavior there is usually an underlying cause and often, a solution. The more youobserve your fish, the easier it will be to identify potential causes of aggressive beavior (and other potential problems) and the quicker you can do something about it, to help all your fish live happier lives.