Goldfish eggs look like tiny, transparent bubbles. The incubation time is 5 to 7 days, depending on water temperature - 70 degrees F or 21 C is best.
During this time some eggs will develop a fungus turn white looking like a very tiny cotton balls. Adding some disinfectants such as methylene blue to the water inhibits the spread of the fungus on the eggs.
On the fourth day eyes and a beating heart is visible on the embryos and begins to wiggle in the eggs.
On the 5th to the 7th day the embryos and yolk sac are more pigmented and the larval burst out of the eggs tail first. For the next 48 hours the 1/5 inch or 5 cm long larvae hangs all over the plants and the sides of the aquarium or pond by sticky head glands, eventually becoming free and swimming off in search of food.