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
(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
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
their own eggs, and the fry as they hatch.