How do goldfish reproduce? As one of the most common and easy to care for household pets, goldfish are a popular starter fish as well as great fish for a community aquarium. They are also widely used as feeders for larger breeds of fish. Though there are many variations, generally goldfish can be classified as Carassius auratus, and their caretaking needs are about the same across the variations. Breeding goldfish capabilities are about the same as well, and for those who are interested, breeding goldfish is a fun and fascinating experience.
One of the biggest difficulties in breeding goldfish is differentiating between the sexes prior to mating. Goldfish can mate when they are a year old, but they don’t really reach prime condition until they are three years old. Once in prime condition and ready for spawning, the females will appear well rounded while the males will develop white bumps called “breeding tubercles” on their fins and around their gill operculum. A ratio of two males to one female in the breeding tank is best to increase the chances of optimal fertility.
In nature or if you go for goldfish breeding in ponds, breeding occurs in Spring, but the conditions that induce spawning behavior can be introduced artificially any time of year. The breeding fish should be in good health and fed high quality food to ensure prime condition and greatest fertility. Keeping the sexes separate until breeding time can stimulate more intense goldfish breeding behavior, and the appropriate tank conditions of the right chemistry, aeration, and amount of water will decrease stress on the fish and improve breeding. The water temperature should be increased gradually over a few weeks to mimic oncoming Spring, until the temperature has reached about 20ºC or 68ºF.
When the conditions are correct and a few days after the sexes are brought together, the males will begin to exhibit spawning goldfish behavior. The spawning chase consists of following after the female and nudging against her abdomen to induce her to lay eggs. This chase can last up to several hours before there are results. When she’s ready, the female will begin laying her eggs in batches. The first batch that she lays is usually the most fertile, but she can lay 500-1000 eggs in a spawning. The male will then spray his milt onto the eggs, fertilizing them.
Once it is certain that the egg laying is done, either the breeders should be removed to their normal tanks or the eggs should be removed and placed into a nursery tank of the same water temperature. If breeders and eggs are left in the same tank, the parents may do some munching on the eggs. The nursery tank should have less than six inches of water, to decrease water pressure enough for the fry to rise to the surface. The optimal temperature for the eggs to hatch is 21ºC or 70ºF, so if the temperature is cooler, increase it slowly. The eggs that are clear are the most fertile, while the darker eggs are the least fertile and susceptible to infection by fungus. Removing the darker eggs and adding methylene blue at the prescribed dosage can decrease the chances of fungal infections. The eggs should hatch in about five days, with the hatching cycle taking a couple of days.
After hatching, the fry will be absorbing their yolk sac for about forty eight hours, so they don’t need to be fed. Once the yolk is absorbed and the fry develop their air bladder and rise to the surface, they should be fed infusorians or very small live food. After about a week, they can be fed finely ground dried fish food. Be careful not to overfeed and to siphon off any uneaten food so as not to foul the tank.
As long as the conditions are right and the proper steps are taken, breeding goldfish can be easy and fun, rewarding a fish owner with an abundance of offspring, which can be sold, used as feeders, or used to fill out personal aquariums and share with other aquarists. So how do goldfish reproduce? With time, patience, and close attention, anyone can have a great goldfish breeding experience.
Check this great youtube video “How to breed goldfish the easy way” by MarineLifeDrew.