How Do You Deal With Aggressive Discus Fish? – [ANSWERED]

Some of the ways you can deal with aggression in your discus fish tank include spreading their food around the tank instead of it being concentrated in a particular area, avoiding overpopulation of the tank, and separating the weaker discus from the bullies.

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Why Is My Discus So Aggressive?

Although discus fishes are generally believed to be very calm and gentle in nature, it is not uncommon that fish breeders have found their discus fishes displaying a certain level of aggression in the aquarium.

NOTE: If you are new to keeping ornamental fishes especially discus, do not be alarmed if you notice your discus exhibiting aggressive tendencies, after all, they are cichlids.

Discus fishes are a kind of fish that flourish when they are in the company of other discus fishes.

So, if one should ask, are discus fishes aggressive? The answer is yes and no, it is not that discus is an aggressive breed of fishes, it is just that they can display signs of aggression under certain conditions.

7 Reasons Behind Discus Aggression

There are seven major reasons that will cause Discus (our gentle-natured cichlids) to display aggressive behaviors, they are:

  1. Tank Domination.
  2. Tank or Aquarium Condition.
  3. Malnutrition.
  4. Breeding Time
  5. Overpopulation.
  6. Feeding Time.
  7. Different Discus Sizes.

[1] – Tank Domination

A discus needs to be in the company of other discus fishes to thrive in the tank.

NOTE: When a discus fish is the only one of its kind in a community tank, the discus fish may die. However, when a school of about 6 discus fishes is in a tank, they might fight for territory.

Like every other kind of cichlid, one of them has to be like the ‘boss’ of the others – the one who goes like, “this is my territory and you cannot move until I say so.” Once one of your discus fishes makes others subservient to him, it usually gets to eat food first before the others and so on.

[2] – Tank or Aquarium Condition

Discus fishes could become aggressive and begin to fight if the condition of the tank is not favorable to your discus fishes. A proper aquarium should have good lighting, plants; especially driftwood (driftwood maintains water pH), and areas where discus could hide since they are very jumpy in nature. If the water quality – pH, temperature – in the tank reduces below what the discus prefers they might become aggressive.

[3] – Malnutrition

When discus is not getting enough food, there is a great tendency for them to become violent and aggressive. The strong have always dominated the weak, therefore stronger or more mature discus will not make it easy for the weaker ones to get food easily.

NOTE: This is very common if a discus pecking order has not yet been established in the aquarium.

So, when you find your discus pecking on each other, not getting enough food could be a reason.

[4] – Breeding Time

When you have Discus in your tank, a time will come when they will start pairing up for mating purposes. Usually, when two discus fishes pair up, they become aggressive towards the others in the tank because they would try to secure any region in the tank where the female discus could lay her eggs and keep it protected.

Specifically, the male discus becomes aggressive in a bid to protect their mates from other male fishes, whereas the females become extremely guarded when it comes to the eggs they lay.

NOTE: Male Discus might attack each other over a female discus fish and sometimes, the fighting could lead to death.

[5] – Overpopulation

If you want to have more than 10 discus fishes in one tank, you should ensure that the tank is a really big one.

NOTE: When your tank or aquarium is overpopulated, the risk of the spread of diseases increases.

In the first point above, I stressed that you can find Discus chasing each other for territory, this is especially serious if the space in the tank is not large enough.

Territorial discus wants a lot of space and they would not take it lightly if they find other discus fishes encroaching in their territory.

5 tips to keep a healthy discus5 Tips How-To
Keep Healthy Discus

[6] – Feeding Time

At feeding time, Discus fish tend to become aggressive with each other and this is very normal behavior based on their natural instincts especially when you feed them blood worms or Beefheart.

[7] – Different Discus Sizes

It is recommended to have at least 5 to 6 Discus in your tank, also recommended to have them all of the same body sizes, because adding smaller Discus fish with the majority bigger size will cause the majority of the bigger ones to bully the smaller ones.

NOTE: Bullying the smaller Discs will put it under continuous stress, which should lead eventually to be infected by different diseases and lead to its death, as continuous stress reduces the Discus immunity system.
13 Reasons
Why My Discus Fish
Is Stressed

How To Solve Discus Aggression And Bullying

Discus fishes, pecking on one another (nipping) can lead to health problems in the tank. When the injuries on the wounded discus fish become infected, the disease could even spread to the other fishes.

NOTE: Always keep an eye on your discus so that any signs of aggression can be detected early enough before it gets too late.

7 Tips How To Stop Discus Fish Bullying

To stop Discus aggression and bullying, apply the below solutions:

  1. Spread Food All Around The Tank.
  2. Aquascaping The Tank.
  3. Avoid Too Deep A Substrate Bed.
  4. Change Your Tank Water Regularly.
  5. Separate The Aggressive Discus From The Weaker Ones.
  6. Amend Decoration.
  7. Keep Discus In Bigger Group.

[1] – Spread Food All Around The Tank

This is very important because it will reduce the rate at which discus fight each other especially if there is already one or more in the aquarium who have marked certain areas as their territory.

When you place food in a single area and it happens that the particular spot has been marked by an aggressive discus fish, the other fishes in the tank will not be able to feed and if that continues for a long period of time, they could die of malnutrition.

Discus Food 101 guide for begineers101 Discus Food
Beginners Guide

[2] – Aquascaping The Tank

When decorating your aquarium, keep in mind that aggressive behavior could be depicted in the tank and you need to make provisions for that. Your aquarium should therefore have a lot of gravels in it.

NOTE: The gravels in the tank can cause some serious injury to your discus fishes and you should therefore be careful to choose gravels whose edges are not very rough.

You should have a lot of driftwood in your aquarium as well – this will make it easy for discus fishes to map out their territories. Besides creating territories for the various discus fishes in your tank, driftwood can give your aquarium a beautiful look.

How Do You Set Up A Discus Aquarium - A Step By Step Guide17 Steps
How To Set Up
A Discus Aquarium

Having a lot of plants that could serve as cover for weaker discus against aggressive ones is necessary in the tank. Your discus fishes could hide behind those plants whenever they are being chased around by bigger ones.

NOTE: When choosing plants for your aquarium or tank, it would be better to use live plants – not only will they make your tank look natural, but they will also supply oxygen to the water in the aquarium.
13 Best Discus Aquarium Plants13 Best
Discus Aquarium Plants

Of course, the idea of aquascaping your tank will take a lot of time to get right – you will have to keep doing things to find out what works.

discus tank requirements 8 tank designs8 Best
Discus Aquascape
Designs Ideas

[3] – Avoid Too Deep A Substrate Bed

Ensure that the substrate you use in your aquarium is not too deep. It does not matter whether you are using soil, gravel or both as substrate, keep the depth at 2 inches. The reason for this is so that when you want to clean out your tank, you will find it easy to remove debris or waste from a substrate of that (2 inches) depth rather than one that is at 4 inches.

[4] – Change Your Tank Water Regularly

Although this is done for many reasons especially one which makes the aquarium a conducive environment for your discus fishes, changing your tank water daily also plays a role in decreasing aggression in the tank. It is just as important as all the other tips for reducing aggression in a discus tank.

NOTE: The waste build-up in the tank will lead to an increase in ammonia levels in the tank and this can be stressful for your discus.

In a stressful environment, it is not uncommon to find discus attacking each other. Clean aquarium water means that your stronger (more mature) discus fish will be less inclined to display any aggressive tendencies toward the weaker ones.

How Do You Keep
Discus Water Quality

[5] – Separate The Aggressive Discus From The Weaker Ones

Use a divider to separate the weaker discus in the tank from the aggressive ones. Although if this is done, there is still a chance that the discus fishes that are kept together could start fighting each other for territory or food. The strong will dominate the weak and a pecking order will be established.

NOTE: The pecking order is what decides which discus gets to eat food first.

[6] – Amend Decoration

From time to time, modifying your aqua scaping design and play decorations around should definitely reset the territories assigned by some Discus in the tank, and keeping your Discus fish in a new environment will always reduce their aggression.

[7] – Keep Discus In Bigger Group

As I always say on the Discus Rescue website, Discus should be kept in a group of at least 5 to 6 Discus in one tank, however, if you have a big enough Discus tank, you better increase this number of Discus which should lead eventually to reduce aggressiveness between them.

NOTE: Smallest tank size for Discus is 55 Gallons to have a maximum of 6 Discus in it, if you want to have more Discus then you have to go for a bigger tank size, remember, the tank size rule is: 10 Gallons for every Discus.

Here is a nice video talking about Discus aggression.

Why Is My Discus Fighting?

There are many reasons why Discus could be fighting each other, they include poor conditions in the tank’s water, territory, malnutrition, breeding time, and overpopulation.


Among all the cichlids, discus fishes are the gentlest. However, they tend to display aggressive behaviors occasionally. The reasons for this may include shortage of food, overpopulation, poor tank water conditions, tank domination, and breeding time.

Some of the ways to prevent aggression is to spread food around the tank rather than placing food in a single spot, separating weaker discus from stronger ones, changing the tank water, cleaning of the tank, and aquascaping.


This is me Firas Sameer, the founder of, I am an aquarist guy with a passion and love for Discus fishes, I am learning every day with my hobby at home and sharing the things I am learning from my experience with you.

One thought on “How Do You Deal With Aggressive Discus Fish? – [ANSWERED]

  1. I have a 75 gal. Tank with 5 discus and 2 Plecos . Two of the five discus were just recently added. For whatever reason they were not eating. I raised the temp to ninety degrees and after a few days they started eating . So after four days I lowered the temp to 86 . That’s when the red panda discus became aggressive. I will try to raise the ph and hope the aggressiveness will stop. I had changed the aquascape just before I raised temp. At first it seem to help but not for long.if there’s any advice that can help I would appreciate it. Thanks

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