Once a year all the coral species spawn en masse on the same night.
Coral spawning is a nocturnal phenomenon that happens annually in late spring or early summer, usually between October and January, but most commonly in November or December. The corals simultaneously release masses of pink eggs and sperm into the waters to form larvae.
It occurs with the phases of the moon and the dates vary, usually 3-4 days after the full moon.
Coral spawn is often confused with plankton blooms called trichodesmium. Trichodesmium, also called sea sawdust, is normally a red/brown color, floats on or near the surface and often found in large streams. It is a natural phenomena caused when the water is warm and conditions calm.