There are more than 1,000 sea anemone species found throughout the world’s oceans at various depths, although the largest and most varied occur in coastal tropical waters. They run the full spectrum of colors and can be as small as half an inch (1.25 centimeters) or as large as 6 feet (1.8 meters) across.
Some anemones, like their coral cousins, establish symbiotic relationships with green algae. In exchange for providing the algae safe harbor and exposure to sunlight, the anemone receives oxygen and sugar, the bi-products of the algae's photosynthesis. They form another, more famous symbiotic alliance with clownfish, which are protected by a mucus layer that makes them immune to the anemone's sting. Clownfish live within the anemone’s tentacles, getting protection from predators, and the anemone snacks on the scraps from the clownfish’s meals.