Goldfish Reproduction

Kelly Roper
A pair of goldfish

Are you interested in goldfish reproduction? Whether you want to breed goldfish yourself or you're just curious about how it all works, learning about how these fish reproduce can be entertaining as well as enlightening. At the very least, you'll learn what your colorful little fish went through on their journey to you.

About Goldfish Reproduction

Goldfish are egg layers rather than live bearers. So, breeding them and actually getting the baby fish, also known as fry, to hatch is more of a challenge than watching guppies give birth over and over again. Still, the experience can be personally, if not financially, rewarding.

Telling Males from Females

The differences between male and female goldfish are very subtle, and you usually can't spot them until the fish are mature. Males tend to have tiny tubercles around their heads, gills and front of their pectoral fins that become more pronounced when they are in breeding condition. Females tend to be a little plumper overall, but if you look at them from the top, they also stick out a little more on their left sides. This gives them a slightly uneven appearance, and it's usually the easiest way to tell the sexes apart.

Spawning Behavior

When water conditions and the temperature are right, the fish will begin to spawn, and it's not difficult to spot when this takes place. If you happen to have at least one male and one female in your tank, you'll notice that the male begins to chase the female relentlessly.

The female will look plumper than ever because she is filled with eggs. As the male chases her, you'll see him press his head against her whenever he catches up with her. This is his way of trying to get her to release her eggs. Look closely at the female's vent. When she's ready to release eggs, you'll notice that her vent protrudes more than it normally does.

When the female releases her eggs, the male releases his milt, and this fertilizes the eggs. As the eggs drop down in the tank, they will stick to any surface they touch, and this is where they will stay as they develop over the next several days. Many breeders recommend that the tank be completely bare of gravel or ornamentation, while others like to use live plants or spawning mops as a surface on which the eggs can collect.


Once the eggs are laid, you must separate the parents from them or they will eat the eggs as quickly as they can. It's usually best to leave the eggs where they are and transfer the breeding fish to another tank. In about five to seven days time, the fry will hatch.

Feeding the New Fry

The newly hatched fry are extremely small and must be fed very nutritious, yet very small food. The fry will become free swimming approximately 48 hours after hatching. After that, begin feeding them newly hatched brine shrimp. You can also feed Liquifry No. 1. This is a high protein, commercially-produced food formulated especially for the hatchlings of egg layers.

As the fry grow you can gradually begin to feed them larger foods like daphnia, frozen bloodworms and powdered spirulina flakes. Eventually they will be large enough to eat premium goldfish flakes and pellets.

The Cycle of Life and Reproduction Continues

With the proper care and feeding, the fry will reach full maturity around age two in most cases. They are then old enough to begin the process of goldfish reproduction for themselves.

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Goldfish Reproduction