These species simply lay their adhesive or non-adhesive eggs to fall to the substrate, into plants, or float to the surface.
The main goldfish varieties are:
Goldfish is considered one of the egg scatter laying adhesive eggs. It is most suitable candidate species for aquarium as well outdoor culture. The secondary sexual characters appear during the breeding season. There is no colour difference between the male and female. Females are typically wider than the males. The male has the tubercles on the head and operculum, when it changes into white, it is ready for breeding.
Prior to one week of breeding, the fishes are fed with live feeds especially Artemia. The breeding tank has to be disinfected with 1-ppm Potassium permanganate. For goldfish breeding, 50 percent ground water and 50 percent pond water is advocated. If possible, place the tank where it can receive sunlight during day time. Place brood fishes in a breeding tank, and do the partial water exchange at about 50 percent.
Eggs are adhesive in nature, therefore to provide substrate the natural plants such as the submerged aquatic plants, or the artificial nests such as the nylon rope (prepared using a split-nylon rope with one end tied). The preferred spawning temperature is 27 – 28oC, but it can be maintained with a water temperature of 20 – 30oC.
For breeding, an ideal sex ratio of male and female is 2:1, which is introduced into the breeding tank during evening hours. While chasing, the male presses its operculum against the female abdomen to fertilize the eggs. The egg laying takes place usually within 6 -12 hrs of pairing.
After spawning, the nests are transferred into the other tank or the brood fishes are removed from the tank. If it is not done, they may eat the eggs to recover the energy lost during spawning. Generally, Female lays about 2000 – 3000 eggs. The eggs are of golden colour and transparent. The transparent area is gradually decreased in fertilized eggs. Unfertilized eggs remain opaque. The hatch-out take place within 3 days, normally it ranges between 80 – 90 percent.