Ethically Sourced. Elkhorn coral (Acropora palmata) is considered to be one of the most important reef-building corals in the Caribbean, although current populations have been decimated by white band disease and have yet to fully recover. This species is structurally complex with many large branches. The coral structure resembles that of elk antlers. These branches create habitats for many other reef species, such as lobsters, parrot-fish, snapper shrimps and other reef fish. Elkhorn coral colonies are incredibly fast-growing, with an average growth rate of 5 to 10 cm (2.0 to 3.9 in) per year and can eventually grow up to 3.7 m (12 ft) in diameter. The color of this coral species ranges from brown to a yellowish-brown as a result of the symbiotic zooxanthellae living inside the tissue of this coral species. Zooxanthellae are a type of algae which photosynthesize to provide the coral with nutrients.