Breeding Goldfish

Breeding goldfish is not easy. Preparation should start before the onset of winter – about four months before spawning takes place in the spring – in order to bring about the optimum conditions for goldfish breeding.

Firstly, make sure the goldfish are mature enough to breed. Any goldfish under 8cm (4″) is probably not ready for breeding.

Then, make sure the goldfish are getting as good a diet as possible. Feed them a broad range of dry and live food.

Next, make sure the water is at a stable temperature of about 18 Celsius (65 Fahrenheit). The reason for this is to bring the water temperature up by a couple of degrees Celsius when the goldfish are ready to spawn. This mimics the natural conditions when winter turns to spring.

Obviously this is easier to control in aquariums than in ponds, however the rise in temperature is more important than the actual temperature, and that should occur naturally in ponds.

Finally, make sure the goldfish that are entering the breeding tank are not the same sex. This previous blog has information on how to tell the sex of goldfish. Better results are achieved by putting 3 males in with 2 females.

The Spawning

When the goldfish are ready to spawn, the male will have the breeding tubercles on his gills. Raise the water temperature by a couple of degrees to 20 – 22 Celsius (68 – 72 Fahrenheit).

When spawning takes place, the female goldfish will lay hundreds, possibly thousands of eggs in the water. They are sticky and need something to stick to. Spawning mops or plants need to be in the water for the eggs to adhere to.

After the female lays her eggs, the male goldfish releases milt (sperm) to fertilize the eggs, and the water goes cloudy.

About 3 or 4 hours later, everything will be over and the goldfish eggs should be removed from the aquarium. This is because the adults will eat the eggs, and if left in long enough, they will eat the newly hatched goldfish too.

Incubation and Hatching

Place the plants/spawning mops with the eggs into shallow water and check them a few hours later. Unfertilized eggs will turn white and need to be removed. They can develop fungus which will spread quickly if they are not removed. Fertilized eggs are a transparent orange-brown colour.

Depending on the water temperature, the goldfish eggs will hatch between 5 and 7 days later (warmer water for shorter incubation period). When the fry first emerge, they are still attached to and feeding from their yolk sacs.

They will feed from the yolk sac for 3 days, during which time it is very important not to feed them. Once the yolk sacs are finished, the young goldfish will be very hungry.

The best diet is a balance of live feed (daphnia and brine shrimp), powdered food (dried flakes and hard-boiled egg yolk) and liquid feed (available in pet shops), 3 times a day. As with all goldfish, take care not to overfeed and polute the water.

And that is the hard part of breeding goldfish over. After the young goldfish are established solid food eaters, all that remains is to nurture them. Don’t overcrowd an aquarium with them, don’t use strong pumps, and stick to good aquarium management techniques to become a successful goldfish breeder.

4 Responses to “Breeding Goldfish”

  1. The Goldfish Guy Says:

    Great article on goldfish breeding!

    Very informative and you provided step by step instructions on how the average goldfish enthusiast will be able to breed their goldfish.

    Great job! Well done.


    Jamie Boyle
    The Goldfish Guy

  2. Ruby Cookie Blue Says:

    How do you keep the water warm?

  3. Birdie Says:

    Great article,easy to understand and to read! Preparing new tank for our eggs,my little girl is very excited.There are over 100 eggs that are viable,so fantail black bulgey eyes babies here you come!!!!!

  4. Becky Says:

    I have an outdoor pond with comet goldfish. The temperature swings from day to night can be up to 30 degrees and it seems this doesn’t deter the breeding process at all. I assume the adult fish eat a lot of the eggs and frye, but still many survive. My only question is how to make them STOP breeding!

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