Found exclusively in shallow coral reef habitats in coastal regions of the Indian Ocean, the Powder Blue Tang is a distinctively marked herbivorous fish that feeds on algae, using its elongated snout and narrow, sharp-tipped teeth to scrape it off of rocks, corals and other hard surfaces. In doing so, members of this species serve a vital function within reef ecosystems, cleaning algae off of coral and ensuring that it does not prevent sunlight from reaching the coral’s dinoflagellates (microscopic organisms that live in the coral’s tissues and produce nutrients through photosynthesis, sustaining both themselves and their coral hosts.) As algae is their sole food source, Powder Blue Tangs populations vary considerably depending on seasonal variations in algae abundance, and this drastically alters their behaviour and lifestyle; when food is abundant they are highly social (living and feeding in large schools) and travel freely around their home reef, but during periods of algae scarcity they become solitary, territorial and highly aggressive towards other members of their species, defending a small algae-supporting area by chasing or biting any other tangs that come near. When algae abundance allows for it gathering in schools provides members of this species with protection from larger predatory fish such as tuna, groupers and jacks, but when threatened lone individuals may still avoid predation by taking shelter within the reef, or attempt to defend themselves using a pair of sharp-tipped scales at the base of their tails (a characteristic seen in many members of the surgeonfish family, known colloquially as the fish’s “scalpel.”) Powder Blue Tangs breed when food is abundant (with females producing buoyant eggs that float to the surface and hatch within around 24 hours of being externally fertilized by a male,) and unlike many members of the surgeonfish family in which juveniles have wildly different markings to adults members of this species have fairly consistent markings throughout their entire lives (although it has been noted that their blue bodies may become paler as a result of illness or stress.)