Living coral polyps in turn grow on top of the skeleton and in this two-step process of calcification, the reef area gradually expands over the successive generations. For this reason, stony corals are also referred to as reef-building corals.
活珊瑚蟲分佈在骨骼的表層，一代接一代的珊瑚蟲不斷分泌堆積碳酸鈣，而形成面積廣大的礁石，石珊瑚就是所謂的「造礁珊瑚」。