How to Breed Fancy Goldfish

Goldfish are one of the most well-known aquarium fish in the world. They are undemanding and many varieties are available ranging from cheap feeders up to mesmerizing strains with various colors, fin shapes and even bizarre anomalies bred into them. However, despite their hardiness in aquariums, they are a somewhat difficult fish to breed in captivity. But with some research, space and money, they can be bred in captivity.

Things You'll Need

  • Two fish tanks, one 20 gallons and other at least 29 gallons
  • Fish tank divider, designed to fit the 29 gallon-tank, available at pet shops
  • Aquarium heaters and thermometers
  • Spawning mops
  • Sponge filter
  • Air pump, airline tubing, air stones and air valves
  • Hard-boiled eggs, oatmeal
  • Commercial fry food (optional)
  • Small live food (optional)
  • Baby brine shrimp
  • Fish ponds or large aquariums with power filters.
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Instructions

    • 1

      Select your goldfish. You will want a minimum of one male and one female. Goldfish are mature when they are three inches long, but still are hard to tell apart by sex. Males in breeding condition have tiny white bumps on their heads and females tend to be rounder. Place them in the 29-gallon breeding tank.

    • 2

      Separate your goldfish with a tank divider and drop the temperature to around 50 degrees Fahrenheit. Raise the water two degrees per day until you reach 68 to 70 degrees. This simulates spring, which triggers spawning.

    • 3

      Set up the spawning tank. This tank should be 20 gallons in size, with water from the breeding tank. The water should be 70 degrees but should not be more than six inches deep. You should only filter it with a sponge filter. Adjust the filter's airline tube with a valve so that there is very gentle water movement.

    • 4

      Add the spawning mops to the tank and remove the divider. If the goldfish are ready to spawn, the male will engage in a "spawning chase" where he pursues the female. They will release eggs and sperm ("milt") during the chase. This will last several hours.

    • 5

      Remove the spawning mop when the fish have finished chasing each other. The tiny white eggs will be visible. Place the spawning mop in the breeding tank (the 20-gallon tank). You can physically pick up any eggs that missed the mop with your hands if you are extremely gentle.

    • 6

      Observe the eggs. Eggs typically hatch withing three days at 70 degrees. Remove any unfertilized eggs (fertile eggs will have a black dot) or any eggs that appear fuzzy. Fungus can spread from unfertilized eggs to healthy eggs.

    • 7

      Begin feeding the fry (baby fish) after the first 24 hours. They live off their yolk sack in the time before this. You can either feed a mixture of finely-ground hard-boiled eggs and oats, live food or commercial fry food. Remove any uneaten food as it will begin to foul the water. Feed at least three times a day.

    • 8

      Start feeding baby brine shrimp at several weeks. The exact time to switch can vary; look at the size of the baby fish. They will be able to transition when their mouths are large enough to eat a baby brine shrimp.

    • 9

      Switch to regular goldfish flakes, ground up, at one month. At four months, they can eat like regular adult goldfish.

    • 10

      Cull or separate out the fish as they grow. Depending on how much room you have, you may need to kill off baby fish that lack desirable characteristics as they grow. If you have a large enough pond of your own, you can simply add the unwanted fry to their as they grow.