How to Tell Male and Female Zebrafish Apart? A Detailed Guide to Sex Identification and Breeding Methods

Telling male and female zebrafish apart is not difficult: male zebrafish have a slender body, large fins, a yellowish body color, a brownish-yellow anal fin, and prominent stripes; females have a more plump body, a paler, bluish body color, a pale yellow anal fin, and an obviously swollen belly during the egg-bearing period.

Zebrafish are egg-laying fish and reach sexual maturity at 4 months of age; generally, 5-month-old fish are better for breeding.

Zebrafish are relatively easy to breed. The breeding water requires a pH of 6.5-7.5, a hardness of 6-8, and a water temperature of 25-26°C. Zebrafish are most fond of eating their own eggs, so small stones and aquatic plants should be placed in the breeding tank to give the falling eggs something to attach to. When breeding, fish can be placed in the breeding tank at a ratio of 1:2 females to males; generally, if they are placed in the tank the evening before, they will spawn and fertilize the eggs by the next morning or noon. After spawning is finished, the brood fish should be removed and kept separately. One female can lay anywhere from 300-1000 eggs each time.

The fertilized eggs hatch into fry after 2-3 days, and after another 2 days the fry begin to swim and seek food; at first they are fed "infusoria", and after 10 days they can be switched to other small live fish food.

The breeding cycle of zebrafish is about 7 days, and they can breed 6-7 times consecutively in a year, with a high egg yield.