​Apart from the zooxanthellae, how else do corals feed?

Not all corals live in sun-drenched shallows, or grow slowly enough to gain all their nutrient needs from their symbiotic algae.

Depending on polyp size, corals catch various planktonic organisms from the surrounding water and will often display a distinctly different appearance at night or when tides and currents bring feeding opportunities. Feeding tentacles equipped with stinging cells enable them to overpower small animals and some of the most remarkable behaviours are displayed by soft corals such as the Elephant Ear Mushroom (Amplexidiscus fenestrafer) which mimics anemones and devours small fish such as clowns which shelter in them.