Glassy Sweeper

Finding glassy sweepers during daylight hours requires searching within shaded structural features along shallow coral and rocky reefs. Divers should peer into caves, deep rock crevices, dark overhangs, and the interior spaces of shipwrecks or harbour structures at depths between 3 and 30 metres. Because these fish aggregate inside confined or overhead environments, divers must exercise precise buoyancy control to avoid colliding with fragile cavern ceilings or disturbing fine silt on the bottom, which can rapidly reduce visibility for the entire group.

When illuminating tight schools tucked inside dark recesses, avoid shining powerful wide-beam dive torches or video lights directly into their large, light-sensitive eyes for extended periods. Instead, aim your torch light slightly off to the side or use a lower brightness setting to observe their gentle, synchronized hovering movements without causing stress. Night dives offer a completely different encounter, as sweepers leave their daytime shelters to float in the open water column high above the reef floor to feed on zooplankton.

Glassy sweepers are resident year-round across their distribution range in the Western Atlantic Ocean and Caribbean Sea. Because their primary habitat consists of permanent reef structures, caves, ledges, and shipwrecks at depths between 3 and 30 metres, their availability to scuba divers does not fluctuate based on seasonal migratory cycles.

Divers visiting tropical and subtropical Western Atlantic locations, including Caribbean islands such as Curaçao, can reliably observe glassy sweepers in appropriate overhangs and caverns during any month of the year. When planning dives to observe these fish, sea conditions, surface clarity, and general regional diving weather dictate the best times to dive rather than any seasonal movement of the fish themselves.

Calm ocean conditions afford easier access to shallow cavern entrances, harbour walls, and exposed wreck sites where daytime aggregations gather. Additionally, night diving during any season provides the unique opportunity to watch daytime aggregations break up as individual sweepers ascend into the water column above shallow reefs to feed under cover of darkness.

The glassy sweeper (*Pempheris schomburgkii*) is restricted to the tropical and warm waters of the Western Atlantic Ocean and the Caribbean Sea. It holds the unique distinction of being the only representative of the sweeper family (Pempheridae) found along the North American coastline, with no members of this family occurring in the eastern Atlantic or eastern Pacific oceans.

Vertically, this species inhabits shallow to moderate depths ranging from 3 to 30 metres. Their microhabitat preferences depend heavily on the time of day. During daylight hours, glassy sweepers rely entirely on sheltered environments, congregating inside dark caves, deep rock crevices, structural undercuts, and sheltered overhangs on both coral and rocky reefs.

They are also commonly found taking cover within man-made structures such as shipwrecks, harbour jetties, and piers. At night, their habitat expands into the open water column immediately above these shallow reef systems, where they float high above the sea floor to hunt planktonic prey before returning to structural shelter at dawn.

The glassy sweeper is a specialized nocturnal planktivore that feeds primarily on zooplankton. During daylight hours, the fish remain quiescent inside dark caves, crevices, and wreck interiors, conserving energy while avoiding diurnal predators. As twilight approaches, their feeding routine begins.

The daytime schools disperse from their sheltered recesses, and individual sweepers swim upward into the open water column high above the bottom over shallow coral and rocky reefs. Equipped with large, well-developed eyes suited for low-light navigation, glassy sweepers actively search for larger zooplankton drifting in the water currents under cover of night.

By rising above the benthic substrate into pelagic zone waters to feed, they efficiently capture planktonic organisms suspended in the water column. As dawn approaches and light levels rise, nocturnal feeding ceases, and the sweepers retreat back into the protection of their daytime caverns and overhangs, completing a daily cycle centered on nocturnal zooplankton consumption.