Corals

Coral reefs are found in tropical waters around the world, primarily because they require sunlight for growth. Tropical waters are generally clear (because they are nutrient-poor) allowing for sunlight to reach the coral reefs.

 

As you already know, within the living tissue of the coral polyp are zooxanthellae, which provide for corals through photosynthesis. In exchange, zooxanthellae receive nutrients and place to live from the coral polyp.

 

 

Furthermore, corals will feed on small creatures floating by. These small creatures are captured by stinging tentacles. Generally during the day, the feeding tentacles are withdrawn into the protection of the hard skeleton formed by the polyp.