Their remains will become part of the reef when they die, supplementing the structure and helping to build a stronger and better reef.
Then you will need Zooplankton - microscopic larvae or animals floating past in the current. At night, coral polyps filter this Zooplankton out of the water to supplement the food supplied by their Zooxanthellae in the day.
If you can get all these ingredients together in a stable environment, for a long enough period of time, you are well on the way to building a coral reef.
The thriving coral polyps will build a skeleton around them to protect themselves from predators. This skeleton is made of Calcium Carbonate, otherwise known as Limestone. Over time, they will build numerous protective skeletons each on top of one another, creating coral reefs (the stunning limestone karsts that dot the landscape of Asia today are actually old coral reefs built in exactly this way).
You can see this very process taking shape if you look closely at a Staghorn Coral. In the tip, you will see a slight coloration - this is where all the many coral polyps live - their colour provided by a pigment within their Zooxanthellae. The branch of Staghorn Coral stretching back from the tip is their skeleton & is made of Calcium Carbonate, or Limestone.
To gel the whole reef together though, you need one more crucial ingredient - a special kind of algae that is beneficial to corals called Coralline Algae. This algae is a little like cement. It fills in the gaps in the reef structure, binding the reef together and making it stronger, so that it can grow larger and is more structurally secure. Without this crucial last ingredient, the reef would more than likely thrive for a while, before collapsing under it's own weight.
If you are able to get all these ingredients together and mix them in the right way, and in the perfect environment, for enough time, you should have a beautiful coral reef. There is no doubting that it is a very tall order indeed though.
Never-the-less, this is what mother Nature has been doing for a very long time now. The first evidence of coral reef structures dates back an astonishing 4 million years. The species of corals that you see today have been in evidence for 25 million years, while many of today's living coral reefs have been growing for up to 5000 years.
Sadly, all this great work is in the balance thanks to the damaging influence of mankind. It is our responsibility to make sure that these beautiful coral reefs, which are responsible for so much life, will be there for the next generation, and the generation after that to enjoy.