Are Discus Fish Aggressive? 5 Things to Consider

Discus fish are not aggressive at all. In fact, you can hardly find a more peaceful fish species among cichlids than the Discus. But it is important to keep in mind that they are still cichlids. They all somewhat carry the temperament of being aggressive when necessary.

This is also why there is a strict pecking order among Discus fish when you keep them together.

Furthermore, there is always that one fish in the tank among them that is the most aggressive. If you remove him, the next most dominant one is going to take over and so on.

The most aggressive one in the tank doesn’t have to be the male either. Again, although we talk about aggression, this is not a trait that is particularly emphasized in Discus fish. They usually only chase each other from time to time.

If you see this, be happy about it because it only means that your little pets are healthy.

Are Discus Territorial?

By their nature, Discus are not territorial. They are not going to bother any other fish in the aquarium for sure. The only time when they get territorial is when they breed.

Then, they start to instinctively protect their eggs, which includes them being territorial and alert.

After all, they want to ensure that nothing is getting in the way of their fry getting hatched. This is what they got used to out in nature. They also have their own pecking order. The most dominant Discus is going to eat first no matter what.

The bad thing about this is that the last ones in the pecking order usually get bullied. The more Discus fish you have, the lighter their punishment is going to be.

Why did My Discus Fish Become Aggressive?

When they start breeding, it is better to ensure that there is nothing bothering your Discus fish. They are going to become aggressive and territorial only when they are protecting their eggs. During the process of breeding, they are particularly sensitive.

If you keep only 2-3 Discus in the aquarium, they are going to be aggressive towards the weakest one from the start.

In this case, the only way to prevent aggression is to add more of them to the tank or to separate them. The Discus fish is one of those species that you either want to keep alone or in bigger groups.

People usually keep them in a group of 8-12 where it is much harder for them to pick only one individual to bully. Things are going to be peaceful in general if you keep them in such large numbers.

Can Discus Fish Kill Each Other?

During breeding or mating discus fish can become aggressive towards other discus, but usually won’t hurt each other to death, still this can cause a lot of stress, so you need to deal with it

If there are enough Discus in your tank, then they are not going to aggressive to the point of killing each other. Although they might hurt each other a bit, there is nothing to be really concerned of. Nevertheless, your fish are going to be much more stressful during this period.

This is something you will need to deal with if you want them to stay healthy. Stress can cause their immune system to weaken, making them vulnerable to a wide range of diseases.

There are two ways to deal with aggression in a home aquarium and we are going to talk about them below.

How to Deal with Aggressive Discus Fish?

There is a reason why experienced fish keepers strongly advise against keeping only two Discus fish together. The fewer their numbers in the tank, the higher the chance that they are really going to hurt each other.

If you would keep only two Discus together, there is a high chance that one is going to harass the other until it gets weak and sick.

You should buy a group of them if you want to ensure a peaceful environment. In order to keep their aggression at a minimum, buy at least a group of 6 Discus.

Not only that, but you also need to make sure there is enough space for each of them to swim around and hide if they want to.

Since the breeding season is when they are particularly sensitive, it is best to set up another tank where you can separate the breeding pair. Then, once the babies are hatched, you can bring them back to the main aquarium.

Will Discus Fish Attack Tank Mates?

As mentioned above, they are going to be a bit aggressive and territorial towards their tank mates during breeding. Their aggression will be aimed manly towards same-species tank mates.

If there are Guppies, Tetras, Mollies, Swordtails or other peaceful fish in the tank, they are going to ignore them.

They are willing to attack their own kind especially if they are low in numbers. As we mentioned above, keeping only two of them can be deadly. You surely don’t want to find one of them floating upside down in the tank after a devastating fight.

Discus can get extremely ill after being bullied day after day by the more dominant one. That is why you need to keep more of them despite how many other species there are around them in the aquarium.


If you are looking to buy only a couple of fish, then the Discus is not the one you should choose. Either buy only one or spend some more cash and buy a big group of them.

Otherwise, you are certainly going to regret it because there will be no way to deal with their aggression.

You are going to be surprised how peaceful they are in a big group. They are going to chase each other from time to time and that’s all.

In that case, breeding is the only thing you need to be concerned about. Once you notice that they are going to breed, put the male and female into a separate tank and all is going to be fine.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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