Goldfish do not have children. They have fry. A female goldfish at maturity will become gravid (egg-laden) and will be mated by the male goldfish. The scenario is something like this: The males basically beat the snot out of the gravid female until she releases her eggs. When her eggs release, a hormone is released along with them that triggers the male to release his "milt". The milt is basically a cloud of sperm. The sperm attach themselves to the eggs, whereby fertilization occurs. The eggs are sticky on the outside, and will clog up your filter, gum up your pump and make a general mess in your tank. After 7 to 10 days (depending on water temperature), the fry (baby fish) hatch out. They basically look like a pair of eyes with a yolk sack and tail. They need to swim up to the top, and break the surface tension to gulp a little air within the first few hours of hatching. This air is used to fill their swim bladder so that they can achieve equilibrium with the water. After another 20 or so days, the fry are actually recognizable as fish, and will start eating something other than paramecium and mashed peas. A word of caution...a goldfish's first spawning will produce 500 to 1000 eggs, of which 100 to 200 babies will survive to adulthood. Subsequent spawnings can be double or more that amount. Make sure you have some friends who want goldfish if you are going to let your goldfish spawn and actually plan to raise the offspring!