Corals are born in a number of different ways, but most often by mass spawning: all of the individuals of a single species on one night a year, releasing all the eggs they've made that year into the water column, packaged into bundles with sperm cells.
Koralji nastaju na nekoliko različitih načina, ali najčešće mrijestom: sve jedinke neke vrste jedne noći godišnje, otpuštaju sva jajašca koja su razvijali te godine u stupac vode, pakirana u paketiće sa spermijima.