Breeding goldfish can be fun but it can also time consuming. There are a few easy steps to prepare the tank for breeding.
1. You will need at least 20 gallons of water to breed two goldfish properly.
2. You will need plants in the goldfish tank as well.
3. You will need a male and a female goldfish of at least 3 years old, anything younger and they may not breed and might cause the female to become egg bound.
4. You will need another tank of at least 3 to 5 gallons of water.
5. You will also need Goldfish baby food, but we will get into that later.
Okay, so lets say you have made all the preparations and now you want to breed your goldfish. One of the main things that will need to happen before the goldfish will want to breed is for the temperature to get down to 64*F for up to 4 months. After 4 months at 64*F a slow warming period back to the normal temp of 70-74*F will trigger the goldfish to breed.
Sexing of Goldfish
The first signs goldfish are ready to mate; The male goldfish will get white pimples on the gill coverings and the female goldfish will become very round looking. The Male goldfish will chase the female goldfish around the tank endlessly (sometimes even tearing and hurting her fins). The female goldfish will become very tried and will release her eggs, sometimes by the hundreds or thousands, all over the tank. Most of them will stick to the plants. The male goldfish will spray his milt over the eggs and the tank will get a cloudy appearance (don't change the water!). After about three to four hours the courtship should stop. This is when the hard work begins.
Now that the eggs are fertilized you will now need to remove them from the tank. Goldfish parents will eat anything including there own eggs. You will need to place them in the 3-5 gallon tank you have had ready. This tank should have no more that about 6 inches of water to avoid the goldfish being crushed by the weight of the water. Too much water also makes it harder for them to swim to the surface. You will need a weak filter system such as a small sponge filter to avoid drawing fry into the filter. You need to aerate the water surface and you will also need a heater.
The temperature of the tank will determine the incubation period generally 5 days at 70*F and 7days at 65*F. You will need keep a good eye on the eggs because some of them could wind up with fungus and infect the rest of the eggs. Healthy eggs will look transparent in color. The non fertilized eggs will be white and most likely will get fungus. You will need to remove the fungused eggs.
Credit to "Sakura"
After four days you should see growth inside the goldfish egg, a small black dot in the middle. After or around the seventh day, they will start to come out of the egg and stick to the plants. You will be able to see the yolk sack that they will be feeding off of for the next 3 days.
Now after the yolk sack is gone they will be searching for food a lot. Many goldfish will die because of lack of foods. Goldfish "fry" as they are called, will need very small particles of food such as frozen brine shrimp, micro worms, crushed hard boiled egg yolk, dried flake foods and even liquid foods if you can find them. More on fry foods You will need to feed them 3 times a day (Morning, Noon, and Night), making sure that you only feed the goldfish fry enough food that they are able to eat it all or you will spoil the tank water.
when they start to grow, you might need more tanks to separate them or find some one who wants these beauties.
Credit to "Tithra"
Goldish Spawning Video 1
Goldish Spawning Video
For more information about breeding please go here Breeding by blinky000