Plectorhinchus, the sweetlips, is a genus in the family Haemulidae, with 35 species found in fresh, brackish and salt waters. These fish have big, fleshy lips and tend to live on coral reefs in the Indo-Pacific in small groups or pairs. They will often associate with other fishes of similar species; several species of sweetlips sometimes swim together. They are usually seen in clusters in nooks and crannies or under overhangs. At nightfall, they venture from their shelters to seek out their bottom-dwelling invertebrate prey, such as bristleworms, shrimps and small crabs.

Sweetlips' colouring and patterning changes throughout their lives. Adult ribboned sweetlips (Plectorhinchus polytaenia) develop increasing stripes with age. Juvenile sweetlips generally look quite different from the adults, and often live solitary lives on shallower reef sections than those where the adults are found. Juveniles may be banded or spotted and are usually a completely different colour from the adult. Small juveniles have a strange, undulating way of swimming, possibly mimicking poisonous flatworms as a means of camouflage.