Why Do Angelfish Fight Each Other? Learn How to Stop Angelfish Fighting

5 min read

They are called angels, but their behavior is far from it. Angelfish fighting each other is one of the most common complaints of aquarium owners who house these magnificent creatures.

Generally, you want your aquarium to be beautiful, calm, and peaceful. You would like to wind down after a stressful day by watching your fish swim about peacefully.

You cannot do that if your fish are intent on tearing each other apart. And you wouldn’t want your precious fish to be harmed – or even killed!

Read on and find out why angelfish fight each other. We’ll also look at how to stop angelfish from fighting.

Are Angelfish Aggressive?


Make no mistake, angelfish are aggressive as they get. It is in their nature. You see, they are predatory fish that hunt other smaller fish for food.

It also helps that they are built to be aggressive. They have super slim bodies, which allow them to be fast agile swimmers. Fish with that kind of speed usually use it to harass other fish.

Angelfish attack each other using their mouths and tails as weapons. They use their mouths to bite their opponent and use their tails as clubs.

When they are fighting, it would appear as if they are kissing, but they are looking to inflict damage on each other using their mouths.

And angelfish twitching at each other is a prelude to a confrontation.

In some cases, you could mistake their mating ritual for fighting, since the behavior is almost identical. This is no coincidence, as the female often sizes up the male by being confrontational. A real fight is usually more violent.

Why Do Angelfish Fight Each Other? 

Like most species, angelfish fight each other because they are wired that way. Being aggressive can make sure they get a slice of the pie, the pie being the vital resources that are limited in the wild.

Food is one resource they would fight over – nothing much to explain here.

They will also fight for territory, as angelfish are quite territorial. Owning territory gives a fish claim to the food and mates that enter it. It also gives them an area to breed.

Speaking of mates, that is another thing angelfish fights over: males will fight over females. After forming a pair, the male will protect the female from other males.


Angelfish aggression towards each other peaks when they become sexually mature at about 10 months and are about to breed. When a pair successfully breeds, they will be highly protective of their spawn site and will chase any fish that comes close.

Other times, they may not be fighting over any resource or mate – it’s simply about who is the big guy.   

Angelfish fighting each other is a way to establish social hierarchy. That is why you would often witness angelfish chasing each other when you first set up your tank or introduce some new fish.

This initial squabbling should end after a hierarchy has been established, but sometimes it can continue indefinitely.

Undue changes to their environment can stress them and cause them to act out, leading to in-fighting.

Lastly, it may be a matter of personality. Some individuals are simply troublemakers – true for humans as well as for fish.

Do Angelfish Kill Each Other?

Although rare, angelfish will kill each other if things go really bad and you don’t remedy the situation.

Even if they don’t die from injury, they will from stress. A fish that is stressed all the time does not have a long lifespan.

Also, your fish may not eat properly if it is constantly chased during feeding time, which could lead to malnutrition.

Angelfish are known to eat their eggs, and even their fry, so they definitely do kill each other in that sense.  

How to Stop Angelfish Fighting

Your aquarium isn’t an MMA ring! You shouldn’t stand by and watch your angelfish fight it out. Here are the things you can do to stop angelfish from fighting each other.

Change the Water Less Often

Research shows that angelfish use chemical signals in the urine and bile they excrete to establish hierarchy among themselves.

Earlier, we saw that angelfish fight to create a hierarchy within themselves, but the fight will be over once the dust settles.

However, when you change the water, you also remove these chemical signals, which means the angelfish have to start all over again – which means, of course, more fighting.

You can reduce the frequency of water changes, as well as the amount of water you change – do a 25% water change instead of a 50%.

You can compensate for the reduced water change by getting a stronger filter, extra components such as a protein skimmer, or by carefully monitoring the water parameters.

Reduce the Number of Angelfish or Get a Larger Tank


Overcrowding is one of the biggest reasons for angelfish fighting. If the other fish are in their faces, the angelfish will take it personally.

And fighting for territory gets bad when there is little territory to speak of.

You can remedy this issue by either getting a larger tank or reducing the number of angelfish. The golden rule is to have one angelfish per 10 gallons, while the minimum size should be 20 gallons.

A breeding pair is highly territorial and aggressive, so try to reduce the number of pairs in your tank – anything more than 2 is asking for trouble in a small aquarium.

Put More Plants, Rocks, Driftwood, Etc.

Aquarium décor such as plants, rocks, and driftwood creates visual barriers in your tank as well as some hiding spots. This makes sure that your fish aren’t always in the face of other fish, which often leads to confrontation.

Your fish can use the hiding spots to stay away from aggressive individuals; try to create a nice hiding spot for each angelfish or pair.

These aquarium décor are what you would normally have in your aquarium as they enhance the appeal of it. You can use it to temper angelfish aggression.

Feed Them Well

Ever heard of the term ‘hangry’? Your angelfish will be short-tempered when its belly is empty, leading to fights. 

Make sure you feed them well; you can increase the amount or frequency of feeding.

But be warned though: overfeeding can pollute your tank with organic waste, which can release ammonia upon decomposition. 

Separate Aggressive Angelfish

No matter what you try, some angelfish are just bullies and won’t stop fighting others.

After having tried all the methods to stop angelfish fighting, what you can do is identify problematic individuals and remove them from the tank.

You can put them in a second tank or just give them to someone else altogether if you have the heart for it. 


Angelfish are beautiful creatures, but they tend to be somewhat aggressive towards each other.

Now that you know why angelfish fight each other, you can take steps to prevent it from happening. Use the abovementioned methods to reduce aggression.

Every aquarium keeper dreams of a tank with a multitude of fish that co-exist peacefully with each other; even though it is difficult with angelfish, it is still possible.

Thanks for reading.


Written by:

Pet Aquariums

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