The blackfin slatey or black-foot sweetlips, Diagramma melanacrum, is a species of marine fish in the family Haemulidae. The blackfin slatey is widespread throughout the tropical waters of the central Indo-Pacific region from Indonesia to Philippines and Borneo. This species reaches a length of 45 cm (18 in). Its name comes from its black inferior fins; it also has distinctive black dots on the body which form diagonal lines.