Although they are the chief architects,corals cannot build a reef alone. Many other organisms help make a coral reef. The most important of these are algae, which are essential to reef growth. Infact, some marine biologists think thatcoral reefs should be called “algal reefs”or, to be fair to both, “biotic reefs.” Onereason for this is that zooxanthellae, which are algae, are essential to thegrowth of corals