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Do Goldfish Fight Each Other? (and How to Stop Them?)

If you’re wondering, do goldfish fight each other then you’re in the right place.

In this article, I’m going to answer the same question.

Goldfish will fight each other if you keep them in a relatively smaller tank. Besides, if you’re not feeding enough food to the goldfish then you’ll notice aggression among them during feeding time. Not maintaining the ideal water parameters can also cause aggression among goldfish.

Do Goldfish Fight Each Other? (and How to Stop Them?) image

Though goldfish are very peaceful fish, still, as with any fish, you’ll see aggression among them if their needs are not fulfilled properly.

There could be several reasons why your goldfish are fighting with each other. And the way to stop the goldfish from fighting is first you’ll need to identify the causes. And then apply solutions accordingly.

This is what I’m going to cover throughout the article.

Keep reading.

Why do goldfish fight and what you can do to stop them from fighting?

goldfish image with text "How to stop goldfish fight"

There could be several reasons your goldfish are fighting with each other. 

1. Not housing goldfish in an appropriate tank

If you’re keeping goldfish in a fish tank then there are a couple of things you’ll need to keep in mind when it comes to the size and shape of the fish tank.

Size of the fish tank

Goldfish can grow very fast. And they can grow very large. They can grow as large as 14 inches!

As goldfish can grow very large, if you want to keep goldfish successfully in a tank then you’ll need to keep them in a large tank.

How big of a tank do goldfish need?

A single goldfish need at least a 20 gallon tank!

If you want to keep more than one goldfish then you’ll need a larger tank (more than 20 gallons).

When it comes to deciding on the tank size for goldfish, a good rule of thumb to follow is - 20 gallons for the first goldfish and then 10 gallons each for every additional goldfish.

For example, if you want to keep three goldfish in a fish tank then you’ll need 20 gallons for the first goldfish and then 10 gallons each for the remaining two goldfish. So, in total, you’ll need a 40 gallon tank to keep three goldfish.

Shape of the fish tank

Because of the shape of goldfish, especially in the case of fancy goldfish, they tend to prefer long rectangular tanks than taller tanks.

In a taller tank, as the water is deeper, it creates more water pressure on the body and the swim bladder of the goldfish which makes it difficult for them to swim in the tank. 

Besides, longer tanks tend to have more swimming space which goldfish like.

2. Not feeding enough food to goldfish

When you’re not feeding enough food to goldfish, the fish will compete with each other for food which causes aggression among the fish during feeding time. 

How much food should I feed my goldfish?

You should feed the amount of food your goldfish can consume within two to three minutes.

Besides, if you’re keeping multiple fish in the tank then you should put the food in different corners of the fish tank to make sure that all the fish in your fish tank are actually getting the food to eat.

3. Poor water conditions in the tank 

Poor water conditions in the fish tank stress the fish which causes aggression among them. 

That’s why you should always maintain the ideal water parameters in your goldfish tank.

What are the ideal water parameters for goldfish?

Here’s a table showing the best water parameters for goldfish

Water ParametersValues
NitrateMax 40 PPM
Temperature 68° to 74° F (20° to 23° C)
Hardness (GH)150 PPM

Poor water conditions not only cause stress in the fish but also lowers the immunity of the fish which makes them vulnerable to diseases.

4. Unsuitable tank mates

First of all, you should not keep any other species of fish with goldfish. Or in other words, you should only keep goldfish together.

Besides, you should not keep common goldfish and fancy goldfish in the same tank.

Why keeping fancy goldfish and common goldfish together is not a good idea?

Common goldfish have slender bodies than fancy goldfish which allows them to swim faster than fancy goldfish. 

This can cause problems during feeding time.

At the feeding time, as common goldfish can move faster than fancy goldfish, common goldfish will eat up all the food which can starve fancy goldfish.

Furthermore, as goldfish will be competing for food during feeding time, they will get aggressive towards each other.

Besides, as common goldfish are more vigorous than fancy goldfish, they can harm fancy goldfish while mating.

5. Sick goldfish in the tank

If you’ve a sick goldfish in your tank then other healthy goldfish might see it as a predator because of its changed appearance. And try to keep the sick fish away from their territory by pushing or hitting the sick fish. 

What to do if you have a sick goldfish in the tank?

If you have a sick goldfish in the tank then you should keep the sick fish in a separate hospital tank. 

If you don’t have a hospital tank then you can easily set up one using a plastic tub.

Here’s a video showing how to set up a hospital tank.

6. Goldfish personality

If you are doing everything right in your goldfish tank i.e.- 

  • You are feeding sufficient food to your goldfish
  • You are keeping suitable tank mates with your goldfish
  • And you always make sure that your fish tank water is within the ideal range 

But still, if you see any of the fish is continuously chasing and harassing other fish then in that case, it is probably because the fish has an aggressive personality.

If the fish is so aggressive that it is causing issues to the other fish like injuries or diseases then, in that case, the best thing you could do is to put the aggressive fish in a separate tank. 

You might confuse goldfish mating with fighting

When goldfish mate with each other, they continuously chase each other and continuously hit each other. 

The male might even nip on the tail of the female goldfish. 

And this might seem like they are fighting. 

Here’s a video showing goldfish mating behavior

So if you see similar behavior among your goldfish then, in that case, you don’t need to do anything.

During the breeding period, the male chases female to encourage her to lay eggs.

The male goldfish chasing the female is more commonly known as the “Mating Dance” which will generally go for several hours.

After some time the female will get exhausted and will finally lay the eggs. 

Once the eggs are laid, the male should stop chasing the female goldfish.

Can goldfish kill each other?

Goldfish can’t directly kill each other. However, when goldfish fight each other, it will stress the fish.

Stress causes low immunity in the fish which makes it susceptible to diseases.

If you didn’t spot the disease at an early stage then it might be very difficult to cure the disease. And the fish will eventually die.

How to care for an injured goldfish?

goldfish image with text "How to care for an injured goldfish?"

Generally, goldfish are very social and peaceful fish. But for any of the reasons we’ve covered above goldfish can get aggressive. 

And sometimes the aggression can lead to injuries.

In that case, you’ll need to treat the fish as soon as possible because these injuries can lead to diseases.

And disease can spread quickly throughout the tank!

How to treat an injured goldfish?

Treating an injured goldfish is actually a very simple process!

1. Keep the injured fish in a separate fish tank or hospital tank

First of all, you’ll need to set up a separate fish tank and cycle the fish tank.

You can easily cycle your fish tank instantly using a filter or filter media from your established tank.

Once the fish tank is cycled then put the injured fish in the tank.

There are a few reasons why you need to put the injured fish in a separate fish tank.

With an injured fish there’s always a possibility that the fish will get infected with any disease. And the infection can spread quickly throughout the fish tank.

When a fish is injured its swimming abilities are affected so at feeding time the fish may not be able to get sufficient food.

Besides, other healthy fish can bully the injured fish. And as the injured fish can not swim properly and cannot stay away from other fish, it will be more difficult for the injured fish to rest and recover.

2. Adding Melafix to the fish tank

Once you’ve added the injured goldfish in a separate tank, now you’ll need to start treating the fish.

For the treatment, you can use Melafix (link to Amazon). Melafix is an antibacterial treatment. It will help to prevent any bacterial infection in the injured fish. 

How to use Melafix to treat an injured fish?

You’ll need to add 5 ml Melafix for every 10 gallons of the tank. For example, if you’ve kept the injured goldfish in a 20 gallon tank then you’ll need to add 10 ml Melafix in the tank.

3. Maintain the water quality

When the injured fish is healing, to give the best possible chances for recovery, you’ll need to keep the water parameters of the tank in the ideal range.

Here’s the table showing the ideal water parameters for goldfish.

Water ParametersValues
NitrateMax 40 PPM
Temperature 68° to 74° F (20° to 23° C)
Hardness (GH)150 PPM

When a fish is recovering, you’ll need to keep the tank water as clean as possible.

To keep the fish tank water clean, ideally, you should do water changes in the hospital tank every other day. 

Not maintaining the water parameters in the ideal range stresses the fish which could cause further complications with the injured fish.

If you do the things I’ve mentioned above, you’re giving the best possible chance to the fish to recover.

And after a few days, you should start to see some improvements with the injured fish.


goldfish image with text "faq"

Why are my goldfish hitting each other?

If you see the male goldfish is continuously hitting the female goldfish then probably he is trying to encourage the female to lay eggs. The male generally chases and hits the female for a few hours during the breeding period.

Once the female gets exhausted she lays eggs and then the male stops chasing the female goldfish.

However, if you notice that the male is not hitting the female but it is either males or females hitting each other then in that case they may be fighting each other. 

As I’ve mentioned above there could be several reasons why goldfish fight with each other. And hopefully, the ways I’ve mentioned in this article will help you stop the fighting.

How do goldfish kill each other?

Goldfish cannot kill each other. However, they can fight with each other. If the fish are continuously fighting then it stresses the fish.

The fish can even get injured during the fight and this can cause bacterial infections and other diseases to the fish.

If you didn’t identify and treat the disease early on then this can even cause the death of the fish.

Is my goldfish mating or fighting?

When goldfish try to mate, the male goldfish will continuously chase the female to encourage her to lay eggs. 

Generally, after a few hours when the female is exhausted, she will lay the eggs which then the male fertilize by releasing “milt” which is like the sperm of goldfish. 

The milt can also make the water cloudy. 

If you noticed that, even after several hours goldfish are chasing each other and hitting each other, then, in that case, they may be fighting with each other. 

There could be several reasons why your goldfish are fighting. Generally, goldfish fight with each other if they’re competing for food or if they are kept in a smaller tank. Besides, poor water quality stresses the fish and it can also lead to aggression among them. 


Goldfish can fight each other if you’re keeping them in a smaller tank or if you’re not feeding them sufficient food. Besides, poor water conditions can also lead to aggression among goldfish.

I hope you found the ways I’ve mentioned in the article to stop the goldfish fight useful.

If you do, please share the article.

Happy fishkeeping!

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Prathmesh Gawai
He is the main author and editor at Aquagoodness.com. And he loves to share helpful information on aquarium and/or fishkeeping hobby. Prathmesh has over five years of aquarium and/or fishkeeping experience. Currently, he has a Betta fish tank. He has written hundreds of articles on various aquarium fish species and on fish tank maintenance over the last five years. Connect with him on YouTube here. Learn more about him here.

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