Breeding goldfish is not to difficult. Most people have never had their goldfish breed because their fish have died before they were mature, this has given the impression that goldfish are difficult to get to breed.

Once your fish are about 3 or 4 inches long and a year old they will be ready to breed. There are two ways to go about breeding your fish, either choose the desired males and females and separate them from the other fish, or just let all the fish spawn together.

Assuming you want to breed specific fish, you will have to find which ones are male and which are female. Unless the fish are in spawning season it is rather difficult to tell which are which.

Mature males will develop tubercles over their gills and their pectoral fins (front fins). These are small little white dots which look like pimples. They also look like a normal fish when you look at their shape. Females will lack tubercles and will become fatter when viewed from above.

When the fish are ready to breed the male will begin chasing the female around. He will follow her closely nipping at her body. When this is seen they are ready to spawn.

Fish in aquariums will have a harder time to spawn. Spawning is encouraged by changes in water temperature, current direction and water depth. Changes in more daylight, live food being fed and other life changes will also sometimes encourage spawning. These are all natural things in the wild or in an outdoor pond, but not in an aquarium.

Spawning can happen in a tank with other fish but for best results it is best if they are moved to their own container once they begin to show signs of being ready to spawn. A shallow (9-12 inch) tub which is a couple of square feet will do fine. Floating plants should be added as well, either live or plastic. The fish will try to scatter the eggs in them.

Goldfish will usually spawn in the mornings as the sun is rising. They will continue to spawn for several hours. They may even spawn several times in the next few days until all the eggs have been released by the female.

Once spawning is done the parents should be removed from the tank they spawned in, or alternatively, the eggs can be removed to a smaller container. If you move the eggs you should keep them in the same water since any significant temperature or water quality change can damage them.

Separating the eggs and the parents are important because the fish will eat their own eggs, and the fry as they hatch.