Coral utilizes the organic byproducts of photosynthesis and/or captures prey.
Tropical Coral Species
Tropical shallow coral reef species—those you might typically picture when you think of a coral reef—get as much as 90 percent of their energy from the organic byproducts of photosynthesis thanks to a symbiotic relationship with algae. [a] Most tropical shallow coral species also capture and consume live prey using their tentacles. This type of feeding usually occurs at night. [b]
Because they live at depths which make light penetration—and thus photosynthesis—impossible, deep-sea corals capture plankton and organic matter for much their energy needs.