How to Stop Oscar Fish Fight?

As an aquarist, I never like it when my fish starts fighting each other.

Luckily I got the opportunity to raise baby oscars in my fish tank. Over the years, they became accustomed to my fish.

Even when I had to upgrade their fish tank from 55 gallon to 125 gallon, I rarely saw my oscars fighting with each other.

However, not everyone’s lucky like me.

They must tame their oscar fish to control their aggression in the fish tank. So, up next in this post you’ll find out the real reasons why your oscar fish starts fighting all of a sudden along with some effective ways to control it.

Let’s get started:

Why are My Oscars Fighting All of a Sudden?

Oscar Fish Fight
Oscar Fish Fight

Oscar fish never fights suddenly. They fight either because of their nature, or there’s something fishy going on inside your tank they aren’t liking.

This can be related to –

Why Do Oscar Fish Fight Each Other?

When keeping an oscar fish in your home aquarium, you need to understand that they enjoy swimming around in an ample space.

And when you place them in a fish tank along with their tank mates, you’re restricting their nature of freely swimming in water.

So, when another fish interferes in their limited space, Oscar fish tends to get aggressive and begin fighting with them.

However, don’t get discouraged after witnessing your oscar fish fighting with other fish.

You can still keep them in your fish tank. It’s just that you need a better strategy to keep them with other fish.

Without an effective strategy, they can once again turn violent and start a neverending fight.


But what’s that one strategy to keep your oscar fish within its limit?

The best solution would be to keep them in an aquarium of at least 55-gallon.

And if you feel like introducing a new fish to your home aquarium any day, never forget to add another 20-30 gallons more to make sure it doesn’t lack in space.

Cutting off a fish’s line of sight to another fish is an efficient way to lessen their hostility in the tank.

Why is Oscar Fish Aggressive?

I get it.

You can no longer watch your oscar fish fighting.

But before learning ways to stop their fight, you must understand the reasons behind their aggressive behavior.

Have you ever wondered why a baby oscar never shows aggression?

Baby Oscar Fish
Baby Oscar Fish

It’s because they get quickly accustomed to the fish tank and all its surroundings.

Besides, Oscars are known as aggressive fish because of its capability to eat whatever fish comes into its mouth.

But what would happen if you introduced a fish comparatively more significant than the oscar fish?

Will they attack them?

No, not at all. You’ll rarely see any aggression from your oscar fish.

Are Oscar Fish Aggressive by Nature?

Despite its reputation as a potentially dangerous predator, the Oscar fish is peaceful enough to share his aquarium. It is best for people of a similar size to him who are neither overly passive nor overly aggressive.

Like any given species, Oscars can vary significantly in personality; some may be more abrasive than others.

Will Oscar Fish Kill Each Other?

Fortunately, Oscars will not kill each other.

But if the aggression isn’t managed, it could kill the smaller fish in the tank.

The urgency of the situation calls for immediate action to put an end to their aggression. And going forward in this post, I’ll share some steps to stop oscar fish fighting.

How Many Oscar Fish Can Stay Together?

School of Oscar Fish
Oscar fish fight in School of Oscar Fish

Oscar fish can happily live with 2-5 Oscars in their tank.  Oscar fish are highly gregarious, preferring to live in pairs or small schools.

An oscar fish also need a great deal of room to develop properly. A 55-gallon tank is a minimum size recommended for a full-grown oscar. At least 20 liters of water is required for every extra oscar fish. Caring for two Oscar fish is all needed if you are short on storage.

It would help if you also didn’t try to keep more than 2 oscar fish together, as they are likely to form a pair and ignore the third.

Yeah! That’s strange but true.

Are My Oscars Fighting or Mating? How to Differentiate?

For the past 3 years, one of my friends have been keeping Oscars together in one of my fish tanks.

Lucky him, they always got along well. Hence, making him less worried.

Then one day, he switched them to a bigger tank, and suddenly they started swimming from opposite sides.

And what surprised him the most was they were doing this with their mouths wide open, and no one was willing to back down.

After adding the Oscars to a bigger tank, he thought his job would become easier. But instead, this new situation made us wonder whether his Oscars are fighting or mating.

They may be just trying to claim their territory in the new tank. Though I can’t speak on behalf of Oscars, all I can say is that territoriality is common among aggressive male cichlids.

Or, if I follow what I’ve seen in documentaries, they seem to be trying to establish territory in the new tank by strutting around.
When they’re ready to reproduce, they’ll lock jaws, and you can tell because the Oscars’ mating tubes will be pointing downward.

Do Oscar Fish Play Dead?

Oscars have a unique way of expressing if you don’t like a particular thing in the tank.

They’ll play DEAD by starting at one place without any movement.

If you’re witnessing this for the very 1st time, you may freak out thinking they are dead.

But thankfully, it’s just their general way of pointing out if they need specific changes in their fish tank.

Oscar Rearranging Tank? What Should You Do to Stop Them?

Imagine you’ve done the hard work of putting together a fish tank.

But one day, you wake up, look at your fish tank and notice something strange.

Everything’s REARRANGED!!!

They’ll rearrange your low light aquarium plant, rocks, or every hiding spots you’ve created in your fish tank.

But the question of the primary concern is why do they do this.

Is there anything seriously wrong with them?


Oscars are known for moving things around in their aquariums until they find the perfect spot.

I doubt you could stop him unless you sealed everything down.

You may try putting all your ornaments to slate stone with Krazy glue and then burying it under the substrate.

The other reason your oscar fish rearranges your fish tank is they’re simply bored.

So, it’s crucial for you to always do some fun activity with them and make sure they never repeat this kind of mischevious acts.

How to Put a Full Stop to Oscar Fish Fight?

Now that you understand the reasons behind your oscar fish fighting or pulling a prank on you (by playing dead), it’s looking at some ways you can put a full stop to their mischievous activities. Let’s get started:

Choose the Best Oscar Tank Mates

Oscar fish can live in an aquarium with other fish. However, as pointed out multiple times in this post, your oscar fish will eat any tank mates that are smaller than them and can easily fit into their mouth. 

Other cichlids of comparable size can share an aquarium with Oscar fish. But the silver dollar fish is their finest companion as it can even scare out your oscar fish.

Do not combine Oscar fish with any catfish smaller than medium. The spines will get lodged in his throat and choke him to death if he tries to consume them.

Keep Them in a Large & Suitable Tank

Make sure the fish tank can accommodate a school of fish. Oscar will likely bully and kill any fish you introduce to his aquarium if it is less than 70 gallons.

If you’re going for multiple oscar fish, I recommend you go for at least a 125-gallon aquarium. However, for a single juvenile oscar fish, a 55-gallon fish tank is sufficient.

If you don’t have a clue of raising a baby oscar fish, here’s a quick video sharing some crucial tips on for your juvenile oscar fish –

Baby Oscar Care Guide

Feed Them Nutritious Food

Oscar requires a healthy and nutritious diet to thrive. The natural diet of an Oscar includes other fish, insects, and worms, as well as fruit and vegetable matter.

Fish pellets of good quality are a great addition to any diet. Once Oscar has reached his maximum length, he will require more significant goodies, such as raw shrimp.

Interesting Fact #1: If appropriately fed, your oscar will rarely show any signs of aggression.

Hikaru Y.

Add Multiple Hiding Places

In addition to providing additional food and water, giving your oscar fish more places to hide can help keep the peace. If your fish ever feel anxious or frightened, they will have a haven to retreat.

Rocks, caves, and even plants for new aquariums can all serve as excellent hiding spots. It’s essential to have several different hiding spots available so the fish can pick one that works for them.

Avoid Overcrowding Your Fish Tank at all Cost

Overcrowding is a significant contributor to hostility in fish. This is because fish become anxious in dense populations.

Do not overstock your aquarium. Avoid housing fish of various kinds, and don’t overcrowd the aquarium.

Interesting Fact #2: Overcrowding isn’t just an oscar fish issue. Any fish you add to your overcrowded tank, they can easily get stressed.

Hikaru Y.

Manage Your Oscars Stress

Talking about stress, it’s one of the most significant contributing factors to the increasing aggression of your fish. Fish can become stressed from several factors, including subpar water quality, a lack of hiding spots, and even too much light in their tanks.

It would be best if you did everything possible to lessen the strain on your fish population. It’s essential to keep the tank out of direct sunlight, provide plenty of hiding spots, and keep the water clean.

Avoid Adding an Aggressive Fish with Oscars

Simply put, certain fish are naturally more aggressive than others. Therefore, if hostility is a problem in your aquarium, it may be best to eliminate any aggressive species.

The Texas cichlid, the green terror, and the Jack Dempsey are among the most aggressive fish species. Those who are not proficient fish keepers should not attempt to care for these fish.

Rearrange The Decorations

The ornaments in your tank should be moved about every once in a while. Oscars are territorial fish; therefore, if they believe their territory is being threatened, they may react aggressively and you’ll be forced to witness another oscar fish fight.

When you rearrange the decorations, your fish will be free to explore new regions. There may be a correlation between this and a decrease in hostility in your fish.

Interesting Fact #3: If not done on time, your oscar fish will rearrange your fish tank out of boredom.

Hikaru Y.

Introduce Target Fish to Your Home Aquarium

Another strategy to stop oscar fish fight is to increase the number of target fish in the tank. Targeted fish are typically large and swift enough to avoid being arbitrarily bullied.

Oscars tend to ignore other Oscars in favor of prey fish because they need an outlet for their aggressive tendencies.

The best option is schooling fish like Bala sharks and silver dollars for this job.

As schooling fish stay in a school, harassment of Oscar divides into several fish, so the risk of harm to any particular fish is significantly reduced.

But, be careful. 

If you notice your oscar fish harassing its tank mates, immediately take it out and place them in another fish tank.

Remove Ultra Aggressive Oscar Fish

Oscar fish are notoriously unpredictable. If you’ve been managing oscar fish for quite some time, you would already know this.

When your Oscar fish starts acting aggressively toward the other fish in the tank, it’s time to get him a new home. He primarily engages in fish combat over territory and forage. There shouldn’t be any issues as long as he has enough to eat and roam.

Give Away Your Aggressive Oscar

If none of those above tips doesn’t work in stopping your Oscars aggression, selling or donating your Oscar may be your last resort.

If you plan on selling or gifting your oscar, be sure to warn the new owner of the fish’s aggressive tendencies. This way, they’ll be ready to take on the issue when it arises.

Hopefully, you can lessen your oscar fish’s hostility with time and effort. If you follow the aforementioned steps, you’ll be able to give your fish a secure and tranquil home.

Concluding Lines

I hope ,you were able to put a full stop to your Oscars aggression using these tips. Besides, if you need any help in stopping the oscar fish fights, you can write to us in the comments or send a mail at our official email address – [email protected].