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NUTRITION
Corals are animals (Phyllum cnidarian) and as all animals they are heterotrophs. However, most of them live associated with algae called zooxanthellae. They live in symbiosis; symbiosis is a close relationship in which living beings from different species associate to obtain benefits. In fact, the algae live in the coral’s tissues. The algae give the coral the glucose they have produced by photosynthesis as well as oxygen and in turn the coral provides the algae with a protected place to live as well as carbon dioxide they need for photosynthesis.
But by this interaction, the coral does not get the proteins and other substances they also need to survive and that is the reason why they also feed on other foods, like phytoplankton, zooplankton, bacteria and both inorganic and organic matter dissolved in the sea water.
Biologists say they are polytrophic meaning that they are heterotrophs and also autotrophs because the algae live inside them.
WHEN DO CORALS FEED?
The feeding of corals depends on the temperature, the time of the day, the content of oxygen in the water, the movement of the water and the preference of food or sediment.
Corals will expand and contract through the day and the night, depending how much food they eat.
In the wild, corals feed more actively at night rather than during the day. When corals are introduced into an aquarium they change their feeding habits. This happens because people feed them during the day.