How to Breed Goldfish

Published: 02nd June 2010
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Selecting Goldfish to Breed

Breeding goldfish requires hard work but with the right skills and a bit of luck, it's possible to raise show quality goldfish. In an uncontrolled environment like a goldfish pond, goldfish will spawn; the females will lay eggs and the males will fertilize them. However, there is a high probability the eggs are eaten before they have a chance to hatch. If by chance any eggs do hatch and the goldfish fry are not eaten, more often than not the goldfish will be disappointing specimens. With the possibility of cross breeding and breeding among genetically inferior goldfish, many offspring are brown in color, not the traditional metallic orange.

For better results, a breeding tank allows goldfish breeders to hand pick each male and female to be paired up. Breeders look for the healthiest goldfish with the best physical characteristics and strongest colors. These goldfish are usually selected in the summer or autumn prior to the next years spawning season. Determining if a goldfish is male of female is not easy but during spawning, males will chase females and sometimes grow tiny white bumps called tubercles on their gill covers or pectoral fins. Females full of eggs can have more rounded bodies but in fancy goldfish breeds, it's difficult to tell the difference.

Goldfish Breeding Tank Setup

  • 10-20 gallon aquarium (38-76 liters)

  • Heater set to an optimal 68-70*F (20-21*C)

  • Simple sponge filter to avoid sucking up goldfish fry

  • Airstone to provide water circulation

  • Spawning mops for eggs to attach to

  • Ultraviolet sterilizer to kill fungus growth on eggs (first 48hrs)

  • Siphon with sponge on intake to perform water changes

Prior to Spawning

Male and female goldfish can be kept apart or together. Keeping the males with the females is thought to help trigger the spawning behavior in the males . For female goldfish, Producing eggs takes a substantial amount of energy; they should be fed a diet rich in protein to get them through spawning. When spawning conditions are optimal and the males actively chase the females, the goldfish should be paired off and placed into a breeding tank.

Raising Goldfish Fry

The female goldfish will lay her eggs on the spawning mop and the male will follow behind and fertilize the eggs with his milt (sperm). Within hours the fertilized eggs will begin to develop embryos and the unfertilized eggs will turn white and die. The parent goldfish should now be removed from the tank so the goldfish eggs are not eaten. Depending on the water temperature, the eggs will hatch in 3-7 days. The hatched embryos will eat the remaining yolk sac, swim up to the surface, inflate their swim bladders and become goldfish fry. The fry should be left alone for two days before being fed. The water can become dirty quickly and bi-weekly 25% water changes should be done.

The goldfish fry should be fed liquid food containing microorganisms or freshly hatched brine shrimp. Over the first two weeks the fry should be fed ever four hours. The fancier breeds can be fed slightly less often. After the second week the fry should be fed micro-worms twice a day, in addition to their other food. The food should be allowed to stay in the water to allow all the fry to feed.

Around the one month the goldfish fry should be examined. The best specimens should be kept and the defective, low quality fry should be culled (removed from the gene pool). These rejects can be fed to larger goldfish, given away to friends, sold to dealers, or euthanized. The selected fry should continue to be heavily fed a diverse diet to encourage a balance growth.

Over the next several months, a power filter should be added when the fry become stronger swimmers. Culling should continue to go on until there are only 6-10 quality goldfish. 50% water changes should occur on a bi-weekly basis. The best results occur when the fry are heavily fed and the water parameters are optimal. It's common for less than 1% of all eggs to become show quality goldfish, if any.

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