Corals are in the phylum Cnidaria, the members of which have radial symmetry. There are a total of 49 species. One way that they get energy is through a symbiotic relationship with zooxanthellae. They are a yellow-brown algae that live in the interior of the coral skeleton. The algae provide energy for the coral and the coral provide protection and access to light for the algae.
Corals can also capture zooplankton as a food source by suspension feeding.
Almost all feeding takes place at night so that their tentacles can be retracted during the day when predators could harm them. Also, photosynthesis takes place during the day and tentacles could prevent light from reaching the algae. Reproduction Corals can reproduce sexually and asexually. Fragmentation can allow for asexual reproduction. Pieces of coral are broken off by storms and animals and they are scattered to new areas where they can grow.