### Identification The Desjardin’s Sailfin Tang (*Zebrasoma desjardinii*) is a true architectural marvel of the reef. Reaching up to 16 inches, its body is a compressed, deep disc, but its silhouette transforms entirely when it flares its gargantuan, sail-like dorsal and anal fins. Look for a sophisticated palette: the body is draped in vertical charcoal-grey bars interspersed with glowing orange-yellow stripes. To distinguish it from its nearly identical Pacific cousin, *Z. veliferum*, look closely at the underbelly and snout; *desjardinii* is uniquely adorned with a fine "stardust" of white or golden spots that break up the linear pattern.
### Habitat & Range This species is a specialist of the Indian Ocean, ranging from the vibrant coral gardens of the Red Sea down to South Africa and east toward Java. They are most at home in sun-drenched lagoons and on outer reef slopes, typically patrolling depths between 2 and 30 meters where light penetration is highest.
### Behaviour & Diet Observing a Desjardin’s is like watching a busy gardener. They are diurnal "lawnmowers," spending every daylight hour grazing on filamentous algae and macroalgae. Using specialized, comb-like teeth, they nip at the reef substrate, preventing algae from choking out the coral. While juveniles are shy and retreat into branching corals, adults are bold and territorial, often seen in pairs or small, loose aggregations. When defending their patch, they snap their fins open in a dramatic "accordion" flash to intimidate rivals.
### Fascinating Fact While they are famous herbivores, Desjardin’s Sailfin Tangs possess a surprising "secret" menu: they are among the few reef fish observed actively hunting and eating certain species of stinging jellyfish and colonial hydroids, proving they are far more adventurous eaters than your average grazer!