Blue tang

Fertilized eggs, that measure up to 0,8 millimeters, hatch within 24 to 26 hours.

An excerpt from the article 17 facts about blue tang
Juveniles are called larvae and occupy the coral habitat until they mature. Maturity is not measured with age, but with size–females are considered mature when measuring 13 centimeters, and males when measuring 11 centimeters.