The most notable features of Bluefin Killifish are the wide zig-zagging black strips that run from the tip of the snout to the base of the caudal fin and the thin black stripe that runs from the base of the pectoral fin to the anteroventral edge of the caudal fin. Males have black pigment along proximal dorsal and anal fin rays, and the dorsal, anal and caudal fins are often tinged red at the base. Breeding coloration in males includes red caudal fin, bright sky-blue dorsal and anal fins and the skin dorsal to the anal fin is pale purple. During the breeding season, the males will display their fins to competitors by flaring their fin rays. These fish grow to a total length of 2 inches and have 9-12 dorsal fin rays.