12 Ways To Tell If Your Goldfish Are Fighting Or Mating

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Last Updated on 2023-08-05

It can often be hard to tell whether your goldfish are fighting or mating. The moment you see them chasing one another around the tank you may think you took such good care of your goldfish that they are now ready to reproduce.

However, if your goldfish are chasing each other it could also mean that they are fighting and trying to hurt each other. In this article, we’ll tell you how to tell if your goldfish are fighting or whether they’re ready to breed.

How Can You Tell If Your Goldfish Are Mating Or Fighting?

Mating and fighting look so similar it can be hard to tell what exactly your goldfish are doing. However, fortunately, there are some clear differences between the two.

When your goldfish are mating, you’ll notice white spots on your males gills, milt being released by the males, and fish eggs inside the tank. When they’re fighting you’ll notice more signs of injury such as scratches, wounds, territorial aggression and sometimes even biting each other.

What Are The Signs Of Your Goldfish Mating

You should be able to tell for sure that your goldfish is indeed mating. Or you might leave them chasing and fighting each other because you thought it was their mating ritual. To tell that your goldfish are mating, here are the signs you should look for.

1. White Spots On The Male’s Gills

When male goldfish are ready to mate, they get small white bumps on the sides of their gills and the tips of their pectoral fins. The bumps on the side of a male goldfish’s gills are usually called “breeding stars.” It is not clear why male goldfish get breeding stars, but it is a good sign that they are ready to mate.

2. Plumpy-bellied Female Goldfish

Female goldfish carry about hundreds of eggs until it is time to spawn. This makes them look fat and develop a plump, round figure. Most of the time, a fattened goldfish is sexually mature and ready to mate.

3. Males Chasing The Females

To mate, male goldfish will actively pursue any females in the aquarium. This strange behavior from the goldfish could last for hours as males will relentlessly pursue the females. The males do this to get the female to lay her eggs.

4. Males Bumping Themselves To Females

After chasing each other around the fish tank for a long time, the female goldfish will get tired and start to lay her eggs. Males will sometimes bump their heads against the belly of the female to help her lay eggs. This can easily be mistaken as fighting, being aggressive, or bullying.

5. Fish Eggs inside Your Fish Tank

You can tell your goldfish are having babies if you start to find eggs all over your aquarium. After all the chasing and bumping, you might start to see eggs. But your goldfish won’t be done mating just yet.

6. Male Goldfish Releasing Milt

When the female goldfish releases her eggs into the water, the male will fertilize them by releasing his sperm, called “milt,” into the water. This can end up making the whole fish tank a little bit cloudy, but there’s no need to worry as it is perfectly normal, and you don’t need to change the water.

What Are The Signs Of Your Goldfish Fighting?

Goldfish are naturally peaceful fish that can get along with many other fish and interact with them. But not every goldfish is the same, and there are other factors in your fish tank that can make them more aggressive. Take a look at this list to find out if your goldfish is being aggressive.

1. Split Fins

There are a lot of things that can cause your goldfish’s fins to split. Sometimes it’s because of bacteria and infections, but most of the time, it’s because they hurt themselves while fighting with other fish. The goldfish could also get hurt if they try to get away from a fighting fish and swim into sharp aquarium decorations or plants.

2. Scratches On Scales

Most of the time, if your goldfish has scratches on its scales, it’s because it had an ich infection in the past and scratched itself on something. But if you see your goldfish chasing each other and later, one of them has scratches on its scale, this is a very good sign that they are fighting and being aggressive.

3. Wounds

When you start to see cuts on your goldfish, this is a clear sign that they are fighting. If you don’t treat a fish’s wound, it could get infected by bacteria or parasites and become very stressed. If you see wounds on your goldfish, you should put it in a separate tank and treat it right away.

4. Biting Each Other

Goldfish are sometimes aggressive and will fight each other even in a large tank if they are competing for food.  This doesn’t always mean that your goldfish hasn’t eaten in a while; it could just be a natural behavior for a goldfish. You can put aquatic plants in your fish tank so that goldfish have a good source of extra food and a place to hide if they are being picked on.

5. Territorial Aggression

Goldfish are usually not territorial and are thought to be some of the most peaceful fish for a tank. But if the conditions aren’t right, they can sometimes show territorial aggression. Most of the time, this happens when their fish tank is too small or when there are too many fish in it.

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Here are some frequently asked questions that people have about whether they’re goldfish are fighting or mating.

Do Goldfish Fight and Kill Each Other?

While goldfish cannot kill each other. If they fight too much it can cause massive amounts of stress which could will end up weakening their immune system and making them susceptible to illnesses which could kill them.

How to Care for An Injured Goldfish?

You can care for an injured goldfish by putting it carefully in a separate hospital fish tank that has the right equipment. Then, keep a close eye on them to see if they are getting better.

When Do Goldfish Start Mating

Goldfish tend to spawn and mate in the spring. When the weather is cold in the winter, and then warmer in the spring, the female’s bodies start to make eggs. But you can make the goldfish think it’s time to mate by putting in an aquarium heater and slowly raising the temperature to around 75°F.


Goldfish are calm, peaceful, and friendly fish, but like any other fish, they can also be aggressive. They can be aggressive over things like territory, food, or just because they want to pick on someone weaker than them. When a goldfish is being mean or aggressive, it usually chases other fish around the tank, which many aquarists may think is a sign that they want to mate.

Your goldfish will be fine as long as you don’t see any split fins, cuts, or scratches on its scales. But if your goldfish shows these signs of aggression, it’s best to treat it right away and keep it away from other fish that are aggressive. As long as you keep an eye on your goldfish and check on them often, they will be safe.

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