According to the belly size of zebrafish, it is difficult to accurately judge when they lay eggs, because they lay eggs. Before laying eggs, although the belly will become larger, it will not be particularly obvious. Breeders have to look at other changes to judge the laying time. Normally, before production, zebrafish's body color will fade, its abdomen will be transparent, some will appear light blue, and its anal fins will turn light yellow. Before laying eggs, zebrafish males will constantly chase females. After breeders find these manifestations, they can put them in breeding boxes for isolation.

Zebrafish females and males will pair themselves in the breeding season, and they will chase each other constantly. After successful pairing, the females will start laying eggs. After the females lay eggs, the males will follow their back sperm and turn their eggs into fertilized eggs. Their breeding speed is relatively fast. They are usually put into the breeding tank the day before and will be reproduced at noon the next day. Zebrafish have the habit of eating eggs. After they breed, it is best for breeders to fish them out immediately to avoid them eating their eggs. In addition, after waiting for a short period of time, fertilized eggs will become transparent, and unfertilized fish eggs will turn white. Breeders need to fish out unfertilized fish eggs to avoid polluting water quality.