How do goldfish mate? And how to make goldfish mate in a tank

How do goldfish mate with each other and how can you tell when they are mating? In this article, we look at how goldfish mate and the ideal conditions for mating. Including how to get goldfish to mate in a tank.

One of the most exciting and rewarding parts of owning goldfish can be seeing them give birth to a new generation of baby goldfish.

Successfully breeding your goldfish shows you have taken good care of them.

And it gives you new baby fish to look after!

While it is possible for goldfish to reproduce in a tank, a lot of factors need to be right for this to happen.

It’s up to you to provide good goldfish care that will ensure your goldfish have the conditions they need to breed.

How do goldfish mate?

Fish mate in lots of different ways. Goldfish mate by chasing each other until the female goldfish releases her eggs.

The male goldfish then releases his “milt”, which fertilizes the eggs.

Assuming the eggs don’t get eaten, baby goldfish will hatch around a week later.

Will goldfish mate in a tank?

Goldfish will mate in a tank. However, to encourage mating, you’ll first need to set up the right tank conditions.

To get your goldfish to mate in a tank, the tank water will need to be stable and properly cycled. The tank should also be large enough to comfortably house two adult goldfish.

The tank should be well planted and should contain at least one male and one female goldfish aged at least three years.

While younger fish can theoretically reproduce, female fish under the age of three are much more likely to become “egg bound”. This leads to eggs that fail to hatch. Even worse, it can potentially cause the death of the adult fish too.

The temperature of the water is one of the most important factors when it comes to breeding goldfish. It’s something that you will need to manage to produce the right breeding environment.

First, keep the tank temperature at around 64 degrees F for four months. Then, slowly warm the tank over the course of a couple of weeks to a temperature of 70-74 degrees F.

This slow rise in temperature will make your fish think it is breeding season.

How do you know if goldfish are mating?

Mating behavior in goldfish is very distinctive. Once you know the signs, you will have no problems spotting it!

The male goldfish will develop small, white spots along their gills (these can often be mistaken for signs of disease, so look carefully!).

At the same time, the female goldfish will become fatter and more rounded.

The male goldfish will then chase the female around the tank.

The aim of this is to encourage the female to release her eggs. The mating “dance” of goldfish is tiring and they will chase each other nearly to the point of exhaustion!

This usually goes on for several hours and may also include the male nipping at the female’s tail and fins.

For obvious reasons, this behavior is often confused with fighting.

Goldfish egg release and fertilization

Eventually, when the female becomes so tired that she cannot continue the chase, she will release her eggs. Many of the eggs will stick to the walls of the tank and to the plants.

The male goldfish will then fertilize the eggs by releasing his “milt” (the goldfish version of sperm) into the water.

This can make the whole tank look cloudy, but don’t worry, it’s perfectly normal and you should not perform a water change.

Fertilized goldfish eggs

Healthy fertilized eggs should be clear in color.

Whereas unfertilized eggs will often develop fungus, which turns them white. Remove any white, unfertilized eggs from the tank, in order to avoid polluting the water.

Once the eggs have been fertilized, it is entirely possible that the goldfish will eat them! To prevent this, you should consider moving the fertilized eggs into a tank of their own. Alternatively, section off the eggs from your main tank so that the adults cannot get to them.

The holding area for the eggs should be shallow so that the water pressure remains low. The flow of water filtration should be very gentle in order to avoid harming the eggs and fry once they hatch. You don’t want eggs and baby goldfish getting sucked into your filter!

Goldfish egg development and hatching

A temperature of around 70 degrees F is ideal during their first five days. After this, you should drop the temperature to 64 degrees F for seven days.

At around four to five days after the eggs have been fertilized, you will begin to see growth inside them! This will appear as a small black spot in the center of each egg.

By day seven, these black specks will begin to hatch. You’ll start to see tiny goldfish sticking to the tank’s plants.

Goldfish only develop their full color as they age, so all newborn fry will appear black or dark gray. And they will be very tiny!

At this stage, you will be able to see the yolk sack that provides nutrition to the growing babies. Once the fry have consumed their yolk sacs, they will become much more mobile and start searching the tank for more food.

Unfortunately, fry often die due to a lack of food during this important stage of development.

You should therefore invest in food designed for fry, such as liquid food or very finely crushed flake food.

You can also feed them tiny pieces of hard-boiled egg yolk shaken in water until it’s almost dissolved. This diet should continue until the fry are large enough to eat full sized pellets and flakes.

7 thoughts on “How do goldfish mate? And how to make goldfish mate in a tank”

  1. What if the goldfish does not release her eggs … she was chased around a lot but now the chasing has stopped but the female goldfish still looks fat like before … what if she doesn’t release her eggs?

    • Hi Heather, thanks for your comment,

      Sometimes this does happen and a goldfish can be what is called “egg bound” where the eggs are stuck, this is notable if your female goldfishes back side looks very swollen.
      Even with frequent spawning the eggs cannot be pushed out, sometimes there is fluid build up that blocks them, or sometimes a clutch of eggs just gets stuck.

      It could also be that they arent actually spawning properly, and are just showing a different chasing behaviour or are preparing themselves to spawn but aren’t in full breeding condition yet.
      Often times the female will keep hold of her eggs until the next spawning.

      If you suspect she is egg bound, then there are a few things you can try, you can try increasing the temperature if they are in a tank, or you can try to gently massage the underside of your goldfish to push the eggs out in an action called milking. Just be very careful as this can cause internal damage to the fish, and is stressful for them, we normally only recommend doing this if you have experience. However, it can be done as long as you are very careful.

      If your goldfish looks really swollen, then I would recommend not feeding them as this can add to the compaction, you could also try melafix or antibiotics to assist if you suspect it is an infection.
      It is not easy to help egg bound goldfish, in most cases leaving them alone is the best thing to do, as it avoids stress and most of the time they can pass the eggs on their own, it just takes some time.
      If they are very swollen however, then definitely stop feeding them or try treatments like melafix.
      hope this helps.

      • Hi! I’ve 2 fantails, and today got a new oranda. They are all small and in a 125l tank, water tested perfect.
        The larger of the fantails is relentlessly chasing the slower oranda about and vibrating up against her (?)
        The fantail has the white spots on his gills suggesting he’s ready to mate. Should I just leave them to it? Or separate them?

        • Hi Ruth, thanks for your comment,
          as long as she can get away from him and isn’t being chased 24/7 I would say leave them to it, although it may cause them a little stress, its a natural behaviour for them, its good exercise and if she does have any eggs store up, it can help release them.

          I would also recommend adding some décor like plants and smooth stones so they can get a break from each other too if you haven’t already.
          If he gets too much and starts tearing her fins or causing her high stress, then you can get an aquarium “breeder box” from most pet stores, its just a floating plastic box with holes which allows water to pass through it, they are really good for separating fish while keeping them in the same water.

          Hope this helps 🙂

  2. I have 5 Toledo goldfish in a 12′ x 14′ pond. The goldfish are 4-5″ long. I had the pond built for bass. Will the bass eat the goldfish or will they co-habit nicely?

    • Hi Wanda,
      It depends what type of bass, a large mouth will nail a goldfish within a second of being added, some smaller species may not eat them right away, but by nature bass are mostly piscivorous fish, meaning their diet consists mostly of other fish.
      They are also aggressive in nature and can be extremely boisterous at times.

      They might not eat your goldfish straight away, but it is unlikely they will co habit nicely and you will probably get issues.
      I personally would not recommend keeping bass and goldfish together at all, but some people out there may have had luck with certain species.
      Hope this helps.

  3. I have a large pond (in Australia) with goldfish. In mid summer I bought a new male gold fish and he won’t leave the female fish (at least 5 of them) alone. Literally he is at it all day every day for the last two months and there have been at least four spawnings that I’m aware of. He is a breeding machine! It is now early autumn and he’s still chasing the girls around constantly. Is this normal? The water temperature varies between 23C and 28C depending on the weather. Is it just a case of waiting for the cooler weather and the water temperature to drop before he gives himself and everybody else a rest? I have so many fry I don’t know what to do with them but I can’t just leave them at the mercy of the other goldfish so they are in a nursery tank, safe and sound!


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