Goldfish Breeding

All goldfish whatever they look like belong to the Carassius auratus family. Before you can start to breed them it is first necessary to ascertain their gender. However this can only be done accurately when they are in a spawning condition. The abdomen of the female becomes fuller and heavier. The changes in the male of the species are clearer and easier to spot. They develop "breeding tubercles", on the gill operculum, and along the front rays of their pectoral fin, and sometimes on the head. These "breeding tubercles", are a white pimple, roughly the size of a pin head. Goldfish mature for breeding at the age of one, but normally they are difficult to sex until they become longer than 8cm, they are in their prime at three years.

Many professional breeders advocate that the fish should be kept in separate tanks before breeding, but obviously this cannot de done before they are sexed. Often breeding is triggered by a change in the temperature of the water. They are actually capable of breeding when the temperature of the water is between 10-26ºC, but the optimum temperature is 20ºC. To achieve this optimum range you can wait for warmer weather or you can raise the temperature of the water in the tank by 2ºC, as it is the change in the temperature of the water which induces the fish to spawn. Goldfish are more likely to spawn in the early morning light.

A slightly higher ratio of males to females also increases your chances of breeding; most people have three males to two females. However remember that goldfish do not like to be overcrowded, as they need a lot of oxygen, which means that every fish needs 15 gallons of water.

When goldfish are ready to mate a “spawning chase” occurs, the male will swim at the abdomen of the female for several hours. When the female is ready she will release her eggs in batches. These eggs will be fertilized immediately by the male, when he sprays milt on them. It is possible for a female in her prime to lay anywhere between 500 and a thousand eggs.

As the eggs have been immediately fertilized, they should be removed from the breeding tank immediately. However bear in mind that they are laid in batches, and the female may not have finished laying, The eggs should be rinsed in aged water that is the same temperature as the water they have been removed from. A heater makes it easier to control the temperature of the water. Once they have been rinsed then they should be placed in a twenty gallon tank, however the water should not be deeper than six inches, this is because at a greater depth the pressure of the water bears down on the fry and it is harder for them to get to the top of the water.

The optimum temperature for the eggs to hatch is 21ºC, so if it necessary raise the temperature of the water. Before they hatch it is a good idea to keep a close eye on the eggs, the ones that are the clearer looking are the most fertile. Infertile eggs can be attacked by fungus activity, and this will spread to the healthy eggs. A few drops of methylene blue can reduce the chance of fungal activity.

When the fish is hatched it will have a full yolk sac, and they are translucent. They do not need to be fed during the first twenty four hours. As they have a full yolk sac, they will invariably sink to the bottom of the tank; do not disturb the fish at this stage. This process of sinking is normal, and once the yolk sac is absorbed, they will develop an air bladder and will start swimming. Once there air bladder has formed they are ready for food. They can be fed on a commercially bought product, or if you prefer a paste of oatmeal and hardboiled eggs can be prepared. The fry need to be fed sufficient food that they can eat in a twenty minute period and any uneaten food should be siphoned off, being very careful not to siphon off the babies as well.

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