How Do Goldfish Mate? All You Need to Know!

Whether you are curious about goldfish reproduction, or you just bought yourself a pair of goldfish to breed, this article will help you learn about how goldfish mate.

Almost every creature on the planet has a particular style of reproduction and learning about it can be very enlightening.

When it comes to goldfish, the mating process results in laid eggs because goldfish do not come under the category of mammals.

It goes without saying that for a successful reproduction process to take place, you need one male and one female goldfish.

But how do you tell the difference between a male and female goldfish?

Identifying Male and Female Goldfish

This can be a challenge because male and female goldfish are very similar in appearance.

This means that the difference between them is very subtle and you cannot really point it out until and unless you are dealing with mature fish.

Here are a few signs that can help you determine whether the fish in front of you is a male or a female:

Male Goldfish Signs

Male goldfish tend to have tubercles around their gills and head.

The vents on their bodies are slightly caved in as compared to a female, and their pectoral fins also become enlarged especially when they are close to their breeding condition.

Female Goldfish Signs

Females, on the other hand, have a more round belly, especially compared to male goldfish.

Just like their male counterparts, they also have protruding vents when they are full of eggs after a successful breeding season. 

How Do Goldfish Mate?

Once the male and female goldfish decide to mate, their spawning behavior is hard to miss.

The Goldfish Spawning Process

When the female is ready, she will begin to look incredibly plump.

Goldfish in general are a bit plump already, but a female goldfish who is ready to mate is much rounder.

That is because her vents are filled with eggs, ready to be fertilized by the male goldfish.

Not only is this a sign for you, but it is also a sign for the male goldfish that she wants to mate with.

Once the male goldfish spots a plump and healthy-looking female, he will relentlessly begin to chase her.

The chasing between the male and female goldfish lasts for a while and is also known to be dangerous because they might hurt themselves if they get too aggressive.

However, once the male goldfish catches up to the female, you will notice him pressing his head against the female from time to time.

This act is meant for the female to release her eggs.

At this stage, you will notice that the female goldfish’s vent will be fully protruding more than her normal appearance.

This is a clear sign that the mating process is just about to happen.

Once the female decides to release their eggs, the male also simultaneously releases his milt.

The released milt enters the eggs and completes the fertilization process.

Slowly and gradually, the fertilized eggs then fall down to the surface of the tank. Since they are sticky in nature, they can easily stick to any surface that they touch.

This helps them stay as they are for the next few days, enabling them to fully develop.

Egg Incubation Period & Hatching

So, how long does it take for the eggs to hatch?

Once the goldfish leaves her eggs, they spend a little time on the floor of the tank.

This time period is known as the incubation period.

Typically, the incubation period for goldfish eggs lasts around 5 to 7 days. That being said, your tank will be filled with little critters in just about a week.

How Many Babies Can You Expect?

According to scientific facts, a female goldfish can lay up to 10,000 eggs in one go.

That’s a lot.

However, that doesn’t mean that you should expect 10,000 goldfish babies crawling around your tank.

Only a very small amount of eggs are fertilized by the milt released by the male goldfish at the time of mating.

The reason why fish eggs hatch in such large numbers is that most of them are expected to die due to their fragile nature.

Some of them succumb to diseases while others may be injured by other tank species or even their own parents.

When it comes to goldfish, it is a known fact that the goldfish parents also attempt to eat the eggs for themselves.

Therefore, with the large number of eggs released, only a few are fertilized, and from those few, only about 30% live long enough to become fully grown goldfish.

Goldfish Breeding Guidelines         

In the previous section, we highlighted the natural goldfish mating process.

If you are planning to breed goldfish at home, here are some important things that you need to understand before you begin.

Optimal Tank Preparation

If you have a single pair of goldfish for breeding, you should not set them up in a water tank that contains less than 30 gallons.

Anything less than this will be harmful to their spawning process and growth.

The bottom of the fish tank should be as clear as possible. However, you can add a few artificial or real plants to give the fish some place to play and hide.

Once the eggs are fertilized, they will slowly drop down and stick to the sides of the tank or the plants. This will give them a safe haven to develop.

Goldfish eggs also tend to stick to the flow, which is why having a bare tank floor is not a bad idea.

If you want, you can invest in a spawning mop (specially made for Goldfish tanks) which will keep the little eggs safe from the parents till you decide to move them to a separate tank.

Filter & Temperature

Other than the correct size, you need to add a filtration system in order to keep the water clean.

The water should be the ideal temperature for your goldfish. Anything too hot or too cold will be harmful to your fish and may delay the mating process altogether.

In their natural habitat, goldfish prefer to begin mating in the spring season. This is ideal for them because the water begins to warm up.

It is important for you to know that the tank temperature should be 50°F.

However, warmer water that goes up to around 74°F can actually encourage spawning between the male and female goldfish.

Remember, do not increase the temperature directly from 50°F to 74°F.

You should gradually raise the temperature, and evenly spread it across a few days till it reaches 74° F.

Second Aquarium

As we’ve mentioned before, goldfish parents tend to eat their own eggs.

Therefore, you will need a second aquarium of a similar size to move the adult parents.

The moving should take place once their spawning process is complete.

If you do not move the parents to a separate tank, there may not be any fertilized eggs left to hatch.

Difference Between Fertilised & Unfertilised Eggs

Since the female goldfish lays a large number of eggs, not all of them are fertilized during the spawning process.

You can easily spot the difference between the fertilized and the unfertilized eggs when they stick to the floor or the plants.

An unfertilized egg will start to appear dark, while a fertilized egg will appear transparent or clear.

These changes will occur over a day or two, so if you want to remove any unfertilized eggs from the tank, make sure you wait around 48 hours before you do so.

What Does Goldfish Fry Eat?

If the spawning process between your goldfish pair is successful, you will have a newly hatched batch of fry on your hands.

Goldfish fry is incredibly small and requires very nutritious food to develop into healthy adults.

Therefore, you must invest in small live food which is usually available at fish pet stores for your goldfish fry.

From their birth to a span of 14 days, you must feed your fish fry Infusoria or a newly hatched batch of brine shrimp.

Once your goldfish fry begins to grow, you can start to feed them larger live foods such as micro worms or daphnia. Even powdered spirulina works well.

Note: Do not feed your goldfish fry pellets or goldfish flakes when they are young. For these kinds of dry foods, you must wait for the fish fry to develop at least halfway through.   

The Bottom Line

The goldfish mating process is not that complicated, especially if you follow all the guidelines highlighted above.

However, you must keep in mind that breeding fish is a big responsibility. Therefore, you must attempt to follow the instructions to the T to ensure healthy mating and hatching, for a healthy batch of goldfish babies.

With nutritious feeding and proper care, you can raise a batch of fully mature goldfish in approximately one year.

This is when they mature themselves and can partake in future reproduction processes.

Hope this helps!

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