Oscar Fish Behavior

Oscar fish are very common aquarium pets in many parts of Europe and America.known for their high intelligence, personality and beautiful colors, these fish have secured their place in the hearts of many sea life lovers.

The behavior of Oscar fish set them apart because it intrigues many people who keep them. They are very social fish, while also managing to be quite territorial. 

However, many scientists hold that Oscars have several behaviors and signals for several occasions in their lives. Just like we have our responses to stimuli and modes of communication as human beings, Oscar fish also have theirs. 

Not so much of communication as just traits that help us know what is going on with them at all times. 

It is the Oscar fish’s behavior that sets it apart from all other aquarium fish. Most people do not fully grasp the essence of this amazing fish personality until they have one in their homes as a pet. A just needs to have one as a pet to understand why people fall in love with this remarkable creature that has all the graceful features of a fish, and at the same time exhibits certain unique traits that human beings

This article will be talking about the different behaviors of Oscar fish, the meaning and causes, what humans can do to fix things up… etc.

Below are possible behaviors that Oscars have and what they mean.

Digging up plants

So you have this really sweet Oscar. You have provided him with a beautiful home in a nice aquarium. Maybe you have decorated this home to the best of your ability with plants and stuff. You are satisfied. 

Then one day you get back from work and to your dismay, the plants have been dug up and uprooted. The place is a mess and you can’t believe your eyes. Did your Oscar do this heinous crime? Well… yeah. It did.

Now let me guess… you are worried. Is the Oscar okay? Is there something wrong with the water? Or worse… is there something wrong with the fish? Or the plant? Why has your pet decided to become this agent of plant destruction?

The answer lies in a very simple fact. Oscar fish are meant to dig. It is something that they cannot really control. They just may have compulsive digging disorder lol. The point is… it is absolutely normal for your fish to dig and uproot plants.

Why do Oscars uproot plants?

They do it for a variety of reasons ranging from

  • looking for food
  • trying to make a proper nest for their eggs. 
  • your Oscar fish may also uproot their plants for no other reasons than they want to.

Is this behaviour harmful to Oscars?

No. Unless the material of the plant is poisonous or they swallow parts of it, your Oscar is going to be completely fine. Try to make sure that every fixture in the tank is secure to the tank. Avoid putting loose objects that can fit into the Oscars’s mouth in the tank as the fish may swallow it and it could cause harm.

What can I do to stop this behaviour in my Oscar fish?

If this behavior bothers you, you could get him an artificial plant instead of a real one and just stick it back in whenever he uproots it. Or you could have it fastened so tightly that he would not be able to uproot it. 

Unfortunately, you cannot make your Oscar fish stop this behavior. Oscar fish are strong and curious animals, and they seem to derive pleasure in pulling up rocks and plants. Why would you want to stop them?

Just make sure that everything is secured in the tank and you’ll have nothing to worry about.

Aggressive behaviour in Oscar fish

Oscar fish are quite territorial. And this means that they show and exhibit a degree of aggression. They are very likely to fight each other due to a bunch of circumstances in their environment or in themselves. 

The aggressive tendencies of the Oscar fish form some of the reasons people seem to live them so much. They spirited way they guard their territories against fish or other animals that they consider as a threat. 

This aggressive behaviour actually shows that Oscars are pretty intelligent and that may be part of why they are so loved by humans.

Why and when do Oscar fish show aggression?

Oscars show aggression for a variety of reasons. It may be due to external or internal factors. The aggression of Oscars is one of the big reasons they are considered intelligent in the world of fish. We will examine the external (i.e: environmental factors) first.

Small or cramped space.

You see… in the wild, there is usually a lot of space for Oscars to swim without necessarily having to get to a fight over territories. If a fight does happen over territories, it is easier for one of the fish to move on and away from that territory and find another. 

But it is not the same when both fish are in the same aquarium. Especially if the aquarium isn’t big enough to give the fish the much needed space. The stronger fish will probably bly the weaker one and cheat it out of food and space. This is likely to spark constant brawls between the fish.


Keep your fish in tanks that are appropriate for their size and number. Fish are meant to move around. Swim around. They need space for that and you cannot cramp three fish in a space that should only hold one and not expect a fight.  

Allow the fish some good deal of space and you may reduce the instances of such attacks on each other. 

Meager food

Right in the same category with space is food. If there is a food shortage or the fish are not getting enough for them both, there will be a rivalry between them and soon, they would attack each other in the fight for food.


The solution to this is obviously to give the fish enough food. Not too much food, but enough food to make sure that they are not hungry enough to peck at each other.

Tank condition

The temperature of the water, the pH of the water, and even the ammonia level of the water can all contribute to whether or not your fish will act in an aggressive manner or not. 

There is a certain balance that Oscar fish need to maintain in order to remain happy in their water. If this condition is not met, Oscar fish may never aggressive towards each other long before they finally succumb to the illness that is bound to come as a result of the unfavorable water condition. 


Keep your water temperature, pH, ammonia level, and rush at the recommended levels. This will help keep your fish happy enough and prevent unnecessary flares of temper.

Smaller fish

Irrespective of whether humans or fish, there will always be bullies in this world. Unfortunately, some Oscar fish do fall into the category. If you keep way smaller fish in the same tank as adult Oscars, the Oscars are likely to bully or even kill and eat the smaller fish. 


There isn’t really much you can do. If your Oscar starts to eat the smaller fish, you need to get him out of there immediately.

Internal factors

Outside of the external factors that can make the Oscar fish aggressive towards each other and other fish, there are also some internal factors that may predispose the fish to it. They are listed and explained below. 


Yet another reason why Oscar fish display aggression is reproduction. It is completely normal for female Oscars to get frustrated or irritated with the male during the reproduction process sometimes. 

Most of these sorts of fights do not result in any serious damage. And even when there has been some damage, it will most likely heal up so long as your aquarium water is in good condition for it. You can notice the female laying eggs and the male fertilizing them even when they fight. 

This will help you know that the “fight” is really more like a lover’s quarrel than a full-blown war between two rivals. It is also important to know that opposite sex tank mates do not get aggressive towards each other quite as much as same sex tank mates. 


It is more likely that two males would fight to the death in the aquarium than a male and a female. So a lot of time, there is nothing to worry about if your ts are of different sexes. 

It isn’t much you can do about this. You will have to wait for the fish to conclude their mating ritual. If it becomes too violent, i.e, the fish have injured each other badly, you can separate them for a while.


Disease and sickness generally make Oscar fish more irritable. However, the funny thing is that it goes both ways. The fish may start to attack other fish because it is irritable as a result of aliment.

However, there are diseases in a sick fish that would make the other healthy fish attack him. This is because an ailment is likely to make the fish weak. This weakness will make him an easy target and thus may get attacked or even killed by the other Oscar in the tank.


Take your fish to the vet to be treated. Make sure he gets the right amount of vitamins. It is really important as vitamin c deficiency can cause this fish to fall terribly sick. 

Try as much as you can to make sure that the fish is in good health and you may reduce the incidence of aggression and attacks on each other. 


One of the things that make Oscar fish so unique is the fact that they have varying temperaments. You may find some that are very calm and friendly towards other fish. And you might also find some that are aggressive irrespective of how favorable the conditions they live in are. 

These fish are just jerks irrespective of whether there is something to fight about or not.  The food may be abundant. The amount of space may be great. The water may be perfect and their health may be sublime and they would still go out of their way to misbehave and attack other fish.

This is yet another thing that you cannot really fix. Oscars have their individual temperaments and you can’t take them to the shrink to get them a therapy. Some Oscars may fluctuate my seasons. Others may seem to have no patterns at all. Some Oscars even have mood swings.

It is always best to separate or isolate excessively aggressive fish. But you could also just move things around the tank a little. A change of scenery has been known to pause the flow of aggression.

You can try revising things in the tank such as moving decorations, wood, rocks, etc…

It may help reduce aggression amongst the fish.

Intentional movement in Oscar fish

One of the things that hold the Oscar fish in high esteem for many aquarium lovers is the intentionality of their actions. They seem to make definite and intentional movements and are not just controlled by the usual flight or fight instinct. It is also never just about food or any other thing. 

A brief observation of the Oscar fish will show you how they seem to focus and make decisions. They don’t just dash around or swim aimlessly. If they have no reason to move, they may just float and hang around. This attitude makes them popular amongst humans because the intelligence behind such behaviour is very obvious. 


Some people call the Oscar fish the “water dog” and there is a good reason for this. These beautiful cichlids are actually very affectionate. It has the ability to recognize its people and show them preferential treatment. Many people actually let their Oscar fish and play with them in the water. 

It is however very important that you don’t just dip your fingers in the water as your Oscar might mistake them for worms and take a snap at it. Instead, bunch your hand into a fist and slowly lower it into the water. 

Let the oscar fish see you slowly unfold the fingers and wait for it to come to you. Try not to move your hand around because once again, the fish may mistake it for prey. Make sure that you do not have any soap or chemicals on your hand before you put it in the water. Also, try not to touch the fish too much as you could damage your Oscars outer protection and cause him to have an infection.

Mood Swings

As absurd as it sounds, Oscar fish have been known to exhibit behaviors that resemble mood swings. The fish could be perfectly fine one moment, swimming and eating happily. And the not could start sulking and refusing to acknowledge anything or anyone. 

There are quite a few reasons that an Oscar fish would sulk. But the major thing to know is that the mood swings in an Oscar fish are often precedented by a sudden change in its life too. 

This could be a sudden drain in its tank water, a change in water temperature or pH level, or it could even be a sudden addition to the tank in the form of another fish or fixture.

The mood swings of an Oscar doesn’t necessarily last as long as that of humans. Your fish will most likely not be sulking for days or weeks so there is nothing to worry about. An Oscar fish should not be sitting at the bottom of the tank for days at a time unless it is sick or there is a problem with the water.

Oscar fish feeding behavior

Oscar fish have an omnivorous diet. But what will really surprise you is the fact that Oscar fish actually could be very funny in the wat they eat. This fish is one of the few that can actually eat food directly off their owners’ hands. 

They know their human family members and recognize precisely the one that feeds them. They would often go to the edge of the water or tank to play and call for attention whenever their humans approached. These cute fish are actually a joy to behold as they dive after food when you feed them one by one.