Here's why:

* Corals are animals, but they don't eat in the way we think of it. They are filter feeders.

* They get their nutrition from symbiotic algae called zooxanthellae. These algae live within the coral's tissues and produce food through photosynthesis. The coral provides the algae with shelter and nutrients.

* Corals also supplement their diet by capturing tiny plankton and other organisms from the water. This is done through their tentacles, which are covered in stinging cells called nematocysts.

So, while they aren't technically carnivores, omnivores, or herbivores, they do consume other organisms and rely on a symbiotic relationship with algae for their food.