Why is coral a heterotroph?

Answer 1

Autotrophs make their own food. Plants and algae and some bacteria do this via photosynthesis.

Heterotrophs gain their food a source other than themselves. Hetero means different. No animal in the world is autotrophic/photosynthesis. Corals (Phylum Cnidaria, Class Anthozoa) are animals, constructions of colony-living polyps (made of calcium carbonate laid down by the polyps) which catch floating microscopic organisms for food. True, corals seem plant-like due to their sedentary nature and some live with symbiotic unicellular algae but the coral animal itself is definitely animalian and cannot provide food for itself via its own mechanism. Corals are definitely heterotrophic.