Depends on the growth rate and destruction rate of the reef structure

Generally, growth rate of a reef (i.e. annual increment towards water surface) is about 0.5 inch per year and each of a well-formed reef is grown over millions years old

Individual corals can grow much faster but these rates do not apply over large areas of reef. Reef growth is not just a factor of how fast corals can grow, it is controlled by many factors, such as death of individual coral polyps, storms, predation by other animals (e.g. crown of thorns starfish) and coral boring organisms