How to Breed Goldfish in an Aquarium

Goldfish breeding began in China about 1000 years ago. According to the American Goldfish Association, goldfish were exported from China to Japan and Korea by the 1500s and to Europe in the 1600s, then to the United States in 1876. Because of natural mutations, there are several different varieties, including the double-tailed goldfish, the Lionhead, the Celestial, and the Bubbleye. Goldfish can potentially be bred at a year old, although they are at their best at three years. Breeding fish is a long-term commitment because they need to be sexed when they get older, which is best done in summer, while breeding itself is generally done each spring.

Things You'll Need

  • Live food such as insect larvae and brine shrimp
  • Terramycin
  • Formaldehyde
  • Copper sulphate
  • 20 gallon tank (bigger if fish are bigger)
  • Filter
  • Plants, spawning mops or coconut fibers
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Instructions

  1. Summer and Winter

    • 1

      Buy your fish during the summer when it's easier to find quality breeding fish.

    • 2

      Look for a female with a heavy rear, bulging left side and soft anal fin. Find a male with evidence of pimple-like nodules on his fins that is a good chaser. Get two males for every female.

    • 3

      Feed your fish live food such as insect larvae or brine shrimp to build strength to spawn in spring.

    Spring

    • 4

      Move the fish to a holding tank or a large pot or bowl for cleaning. For one fish, mix a measure of Terramycin, with 80 drops of formaldehyde and 6 drops of copper sulphate in four gallons of water. Let fish soak for 20 minutes before moving to clean water.

    • 5

      Put together a spawning tank. Get a tank that holds at least 20 gallons. Fill the tank with shaggy plants, spawning mops or coconut fibers. Put the fish in the spawning tank once it's clean.

    • 6

      Wait for fish to spawn. Males will develop nodules on gills and fins and the female's body will grow rounder. The male will start to chase the female around the tank. Once the female lays her eggs the male releases milt on the eggs, fertilizing them.

    • 7

      Remove fish from spawning tank after spawning is complete and put into another tank to avoid one or both of them eating the eggs.