Tetra Fish Care

Are Glofish Tetras Aggressive? Are They Fighting Or Playing?

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If you follow Glofish Tetras more than any other species, you will agree that they have gentle behavior with attractive appearances. Also, they behave well with their tank mates without harming or bullying them. However, some fishkeepers doubt that the Glofish Tetras get unusually aggressive. So, are Glofish Tetras typically aggressive? Or is it an unusual reaction?

To begin, ‘Are Glofish Tetras aggressive?’ – No, Glofish Tetras aren’t aggressive. They are peaceful and cause no harm to their tank mates. But some factors like the non-schooling of Glofish Tetras, illness, mating desire, overcrowded tanks, experiencing bullying from tank mates, and improper tank conditions tend Glofish Tetras to show aggressive behavior. 

Here, the aggressive nature of Glofish Tetras appears due to situational reasons only, not naturally.

Glofish Tetras Behavior

Glofish Tetras are eye-catching Glofish species due to their peaceful behavior and general appearances. Usually, their appearance pulls people’s attention. But their gentle manner makes people prefer them more.

Glofish Tetras are active, gentle, and peaceful schooling fish. They thrive in an aquarium without harming or dominating their tank mates.

As they are schooling fishes, they maintain a healthy manner with each other. Also, you can see Glofish Tetras getting along with other fish species without causing any harm to them.

Are Glofish Tetras Aggressive?

In short, no, Glofish Tetras are not aggressive. They are typically friendly and peaceful fishes, which show no aggression.

But like any other fish species, there is a high chance of Glofish Tetras getting aggressive when they stay in uncomfortable situations. Such situations may occur due to the improper tank environment or the negative impact of their tank mates.

Otherwise, the aggressive behavior of Glofish Tetras is not very noticeable.

Is Aggression In Glofish Tetra A Normal Thing?

Generally, there is no fundamental feature like the aggressive and attacking behavior in Glofish Tetras. These are their uncommon traits, which are visible if they are in miserable situations.

Therefore, aggression in a Glofish Tetra is not a normal thing in them. If you see any aggressive behavior, then they must be in some trouble and requires your help.

Situations That Make Glofish Tetra Aggressive

If you take good care of Glofish Tetras, then the possibility of aggression in them will be very low. Yet, if you notice some aggressive nature in them despite proper care, it is essential to know the reason behind it.

To help you out, I have summed up some situations that usually make Glofish Tetra aggressive or violent. They are:

Non-schooling Of Glofish Tetras

Glofish Tetras are schooling fishes. Meaning, you should put them in a group for their comfortable stay in a tank. They get support from one another that makes them grow better.

Here, if you put Glofish Tetra solely or in a group of less than 5 of them, there is a possibility of growing aggression in them. They get nervous and awkward quickly in such situations. It will eventually make them dull in the tank and later leads to aggressive nature.


Like in any creatures, illness is a common situation that builds up stress and anxiety in Glofish Tetras. Such pressure will further lead them to become aggressive and nasty.

Illness in Glofish Tetras may occur due to an unsuitable tank environment, lack of tank mates, lack of adequate diet, etc. However, sometimes, some genetic issues may lead to sickness in Glofish Tetras.

Mating Desire

The mating desire of Glofish Tetras has often led them to become more aggressive. If there are more male Glofish Tetras and fewer female Glofish Tetras in a tank, the male becomes more aggressive and attacks the other, competing for the female one.

The male Glofish Tetras becomes extra aggressive compared to female Glofish Tetras if their mating desire is unfulfilled.

Experiencing Bullying From Other Tank Mates

Glofish Tetras are peaceful schooling fish. They prefer staying active and cheerful in a tank. In between, if any fish species is offensive or dominating in the tank, the Glofish Tetras will certainly experience bullying from them.

Such an experience of bullying from other tank mates will surely trouble Glofish Tetra. It will eventually make the Tetra aggressive and toxic.

Overcrowded Tank

As Glofish Tetras are schooling fish, they prefer to stay in a group of at least 5. However, it doesn’t mean that you should put them in a large number without considering the tank size.

If you place your Glofish Tetras in a small or large-sized tank, but with numerous fishes, your Glofish Tetras tends to be irritated and aggressive slowly due to overcrowding.

Improper Tank Conditions

If the Glofish Tetras tank lacks to manage requisites like: pH level, water temperature, water hardness, clean water, lighting, decorations, fertilizers, etc., it will severely affect them. By the lack of such requisites, Glofish Tetras believes the tank environment is not safe and comfortable.

Thus, such thoughts make them to be self-protective, which later results in showing aggressive nature.

What Happens When A Glofish Tetra Gets Aggressive?

The aggressive behavior of Glofish Tetras is not a good sign. An aggressive Glofish Tetras affects not only itself but also its tank mates and tank environment.

Hence, here are some outcomes caused due to the aggressive nature of Glofish Tetras:

  1. An aggressive Glofish Tetra will suddenly chase, bully, and attack its tank mates.
  2. The aggression in Glofish Tetra puts more stress and anxiety in itself. It will affect the Tetra’s mental health.
  3. An aggressive Glofish Tetra takes no proper diet and stays hungry for an extended period. While in hunger, it may start eating any random scraps found in the tank, which can be dangerous. Plus, the Tetra might snatch other mates’ diet too.
  4. An aggressive Glofish Tetra affects its tank mates’ health, both mentally and physically. The Tetra gets unusually rude and harsh to them.
  5. The tank environment becomes unhealthy. Every other being existing there would be in trouble due to the act of aggressive Glofish Tetra. Also, they might turn into aggression as well.

How To Control And Prevent Aggression In Glofish Tetra?

If you see your Glofish Tetra acting unusual and getting aggressive, you should know what is bothering him and aid accordingly.

Here are few points that can help you to control and prevent your Glofish Tetras from being aggressive:

  1. Maintain the 6.2 pH levels, 3 to 6dGH water hardness, and water temperature (72 to 82 degrees Fahrenheit) of the tank. If you see any fluctuations, quickly set to the correct point.
  2. Put Glofish Tetras in a group of at least 5 in a tank. You can go for more numbers of Glofish Tetras by considering the tank size. Note: the more numbers of Glofish Tetras in a group, the more comfortable they get and thrive.
  3. Don’t overcrowd your tank. Put Glofish Tetras in a group with other mates by viewing the tank size only. Be cautious, don’t put them in a tank less than a 10gallon tank. Otherwise, they might suffocate.
  4. If you see any other tank mates bullying and dominating Glofish Tetras, immediately separate those species in another tank.
  5. Keep an equal number of male and female Glofish Tetras in a group to prevent an aggression fight, occurs during their mating urge.
  6. Give a proper diet to Glofish Tetras for their healthy life.
  7. If your Glofish Tetra is avoiding food and being inactive, there is a high chance that your fish is sick. To make sure, observe its activities as there exist many signs of sickness. Later, see a fish vet and provide necessary medications.


Glofish Tetras are active and peaceful schooling fish and are friendly with their tank mates. They aren’t aggressive at all. But due to some situational reasons, their gentle behavior can change into aggression.

To control and prevent Glofish Tetra from being aggressive, you must take their proper care.