 Cnidarians feed in several ways: predation, absorbing dissolved organic chemicals, filtering food particles out of the water, and obtaining nutrients from symbiotic algae within their cells. Most obtain the majority of their food from predation but some, including the corals Hetroxenia and Leptogorgia, depend almost completely on their endosymbionts and on absorbing dissolved nutrients. Cnidaria give their symbiotic algae carbon dioxide, some nutrients, a place in the sun and protection against predators.
