### Identification Commonly known as the "Stonewort" or "Shaggy Coral," *Acropora millepora* is easily recognized by its corymbose growth form—it looks like a dense, flat-topped cushion of short, uniform branchlets. While many *Acropora* appear skeletal, this species often looks "furry" because its polyps remain extended during the day. Look for a kaleidoscope of colors, ranging from neon pink and orange to soft green and sky blue. The defining field mark is the radial corallites: they are uniform, scale-like, and arranged in a neat, overlapping pattern resembling fish scales or roof shingles.
### Habitat & Range This is a shallow-water specialist, most at home on reef flats, lagoons, and upper reef slopes across the Indo-Pacific, from the Red Sea to the Great Barrier Reef. You’ll typically find it at depths of 2 to 12 meters, where sunlight is intense and water movement is high. It thrives in high-energy environments where surging waves bring fresh nutrients.
### Behaviour Unlike many "night-owl" corals, *A. millepora* is active during the day. Its polyps emerge to bask in the light, giving the colony a soft, tactile appearance. Socially, it is a pioneer species; it grows rapidly to outcompete neighbors for precious real estate. Once a year, usually after a full moon, these colonies participate in a spectacular "mass spawning" event, releasing buoyant pink egg-and-sperm bundles into the water column in a synchronized underwater blizzard.
### Diet This species is "dual-fueled." It derives the majority of its energy from symbiotic algae (zooxanthellae) living in its tissues, which convert tropical sunlight into sugars. However, it is also a voracious predator; those "shaggy" polyps are equipped with stinging cells (nematocysts) used to snatch microscopic zooplankton from the passing current.
### Fascinating Fact *Acropora millepora* produces its own "sunscreen." To survive the punishing UV rays of shallow water, it creates specialized fluorescent proteins that act as a biological filter, protecting its delicate tissues from sunburn while giving the coral its brilliant, glowing coloration!