The Zebra Danio is a prolific spawner. Females are able to spawn at intervals of two to three days, laying between 300 and 400 eggs each time. If you are considering breeding them, here are few tips that will help:
Tip 1. Have a separated tank for breeding. The parents should be removed, once spawning is complete to prevent them from eating the eggs. A densely planted aquarium is recommended. Keep the tank’s water shallow (four to six inches deep) and place first the females. Wait until the next day to introduce the males. The ideal temperature would be 83.3 °F (28.5 °C).
Tip 2. Make sure you have a group of six or more adults. A good ratio would be one male per three or more females. Females tend to be larger than males and have more subdued coloration. The bodies of males usually have a bright-yellow background with fine red lines between wider blue longitudinal lines. The fry will hatch in two days and will accept small fry foods.
Source: aquarium fish magazine