Complex sentence: The first one is through the photosynthesis of its symbiotic zooxanthellae, living in its tissues, the second by capturing its prey with its tentacles that allow it to immobilize its prey (small invertebrates, fry or juvenile fish).
Split into simpler sentences: The first one is through the photosynthesis of its symbiotic zooxanthellae, living in its tissues. And the second method is by capturing its prey with its tentacles that allow it to immobilize its prey (small invertebrates, fry or juvenile fish).