SweepersPempheridae

Sweepers (Pempheridae) are small, deep-bodied, laterally compressed fishes, typically silvery in colour. They possess large eyes, a small, upturned mouth, a short dorsal fin, and a long anal fin. Most species measure 10-15 cm (4-6 in) in total length, with some growing up to 20 cm (8 in). Their common name derives from their habit of 'sweeping' through protected spaces by day.

By day, these fish form dense, cohesive schools in sheltered, dimly lit areas, including under large reef overhangs, within caves, or inside wrecks. These schools are typically found from 1 to 30 m (3-100 ft) deep. At night, the schools disperse, and individual sweepers move into the open water column to feed on zooplankton. Divers frequently encounter these dense schools, which can obscure large sections of reef structures.