Are Platy Fish Aggressive? Platy Bullying Other Fish and its Solutions

Aggression is a common behavior that most of the living things show against their competitors. Like other animals, tropical freshwater fish such as Platies also show signs of aggression when exposed to some specific situations. If you are worried about this aggressive attitude of your Platies towards other fish, don’t worry as we are here with some solutions for you.

Are Platy fish aggressive? Normally, Platies don’t show any signs of aggression against their tank fellows. They are considered peaceful and non-violent freshwater fish and can live happily with their tank mates like Mollies, Guppies, Swordtails etc. Aggression in Platies can occur with sudden changes in the environment, improper male to female ratio, less hiding spots or by overpopulating the tank.

There are several other reasons that can lead to the aggressive behavior of your Platies. Let us dig in some more and find out some solutions to this problem.

How to tell if your platy is aggressive?

Aggression is most probably the first social problem that beginner aquarists have to deal with. Some fish are dominant in the aquarium and they start to bully the weaker fish. Bullying and aggression may cause stress among the weaker fish and they will be more prone to diseases.

Platies are not necessarily territorial fish but they do want their own specific place in the group. These territories are mostly used to have proper access to food or to impress the females. Therefore, a certain amount of chasing and aggressive behavior is considered normal.

However, if there isn’t enough space between the dominant fish and the other fish in the aquarium, this aggression can be problematic. In this case, the dominant Platy may start to harm the other fish in the group or deprive them of moving around freely. And, ultimately the other fish may end up being harassed, damaged or even dead.

It is extremely important for the aquarists to identify this aggressive behavior in time so that they can nip the evil in the bud. Typically, the first signs of aggression shown by the bully involve flaring its fins or gill covers. This means that the bullying Platy is intimidating the other fish to run away.

As there is limited space in the aquarium, the weaker fish cannot leave the territory of the aggressor. The bullying Platy may respond to it as if it is being challenged and then start chasing and attacking other fish. So, when you see all this going on in your aquarium, you should understand that it’s time for you to take some action.

How to Stop Fish Aggression (Video)

What are the main causes of aggression in platies?

As stated above, territorial problems are one of the most common reasons for aggression among the Platies. But sometimes there are some other factors as well that can contribute towards this bullying nature of the Platies. Some of these factors include;

  • Alpha male attitude of the Platies
  • Improper male to female ratio
  • Pregnancy
  • Overcrowded tank
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Alpha male attitude

Alpha male attitude is the most common behavior trait shown by almost all the creatures in the world. In the case of Platies, whenever the breeding time comes, the male fish start to show aggression and bullying attitude to be the alpha. Female fish are attracted to the strongest candidate for breeding.

The dominant male may misuse its rights and may start showing aggression towards the weaker fish. In many cases, the alpha male may harass the other fish, stop them from moving around or even eat them in extremely rare cases. This may result in the weaker fish getting damaged, stressed, and ultimately, they may die.

Improper male to female ratio

If you have an aquarium with more male Platies as compared to the females, you are paving the way for aggression yourself. When there are more males and fewer females in your aquarium, it means that there will be more fight to spend time with the females.

The male Platies will fight and show aggressive behavior to find out who is the strongest. And, when the dominant male emerges, he will definitely start bullying other fish and ultimately the aggression will elevate.


Pregnancy is also another factor that can cause aggression in your aquarium. Whenever the female fish get impregnated, they may show signs of aggression towards other fish. This may be due to the fact that she wants to protect itself and its baby.

Another explanation of this bullying attitude can be the hormonal issues. The closer they move towards giving birth, the more this aggressive behavior may show up. This is due to the fact that when the time of birth approaches, they may want to stay alone. Therefore, whoever bothers them at this time becomes the target of aggression and potential harm.

Overcrowding the tank

Overcrowding can cause a lot of trouble in the aquarium in addition to aggression. If you have a small tank and have more fish in there, it means that every fish is going to fight for its space. The dominant fish are naturally going to bully other fish due to their territorial issues.

Other than territory, when feeding time comes, the fish are again going to fight for food. Moreover, overcrowding can result in poor quality of water which may increase stress among the fish which in turn leads to aggression.

How to deal with a bullying platy?

If the owners don’t fix things in time, chances are that their fish might end up getting hurt and even dead. Torn fins, damaged mouth and eyes, and secondary infections can be a common problem for you if you have a bully in your tank.

There are a number of ways through which you can fix the aggressive behavior of your Platies. Some of these solutions include;

  • Schooling fish
  • Introducing new fish
  • Rearing fish together
  • Removing the bully
  • Removing the weak
  • Overstocking

Schooling fish

The bullying behavior in schools can be solved simply by adding more fish to the aquarium. One thing to be kept in mind while adding more fish to the tank is their gender. Among species like Platies, mollies etc. where the aggression between males is common, it is a good idea to have at least twice as many females in the tank as males.

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If the schooling species aren’t kept in adequate numbers, the dominant fish will again end up harassing and killing the weaker ones.

Introducing new fish

If you want to introduce schooling fish in your aquarium, it is better to introduce them in the form of a group or a succession of reasonably large groups of similar-sized individuals.

As far as the territorial fish are concerned, it is a good idea to introduce the aggressive species a few weeks after adding the least aggressive ones. This will give each group of fish a chance to claim their territory.

Rearing fish together

If you want a mated pair of tropical freshwater fish in your aquarium, it will be difficult for you to introduce two sexually mature fish to one another. This may elevate the aggression in your aquarium environment.

The best approach in this situation is to rear a group of six or more mature fish together and let them pair off on their own. When you get your desired pair, you can remove the rest of the fish from the tank.

Give the bully a time-out

The best and most common solution to get rid of aggression in the aquarium is to give the bully a time-out. You can put the bully in a separately covered bucket for half an hour and then put it back to the aquarium. This may let the bully believe for a while that he is in a new place. This is a very effective trick to reduce bullies.

Removing the weak

Removing weaker fish from the aquarium is a good step for the ones who are bullied. But this is not a permanent solution as the aggressor will then start picking on the remaining weaker fish in the tank.


Overstocking the aquarium is sometimes the reason for aggression in the aquarium. But, in some cases, this step can help you solve the problem of fish bullying other fish. If you have a high density of fish in your aquarium, it means that no single fish can claim a stable territory.

The only problem with this solution is that it will require a massive amount of filtration and maintenance work from you to keep a healthy environment in your aquarium


Do Platies eat their fry? Platies are livebearers and give birth to fully grown fry instead of laying eggs. Platies usually don’t have any maternal instincts. They may see their fry as food and eat them as they are omnivors. If you want to increase the population of your Platies and want the fry to survive, it is a good idea to separate the fry from their mother.

Which of the tropical fish can live happily with Platies? Platies are considered peaceful freshwater fish and can live happily with other Platies, mollies, guppies, and swordtails etc.

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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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