Excessive sedimentation is a major threat to coral reefs. It can damage or kill reef-building corals andcan prevent the successful settlement of their planktonic larvae. The surgeonfish Ctenochaetus striatus feeds onrocky surfaces by sweeping loose material into its mouth with its flexible, broom-like teeth. In addition, it graspsand removes hard substrates with the aid of its special palate structure. It then transports sediment matter of thereef by defecating the ingested material outside the rocky zone of the reef. We analyzed 150 feces samples ofsix individuals, diferentiating between (1) ingested by sweeping and (2) ingested by scraping, and compared theircontent with inorganic land-derived and marine sediments trapped at the feeding area. Projections based on fishdensities, defecation rates, and quantities as well as composition of sediments collected by traps on the same reefsite suggest that C. striatus removes at least 18% of the inorganic sediment sinking onto the reef crest. Theeroded share in the exported matter is about 13%. This finding points to a hitherto not verified role of C. striatusas a reef sweeper and reef scraper, whereby the first function is by far dominating.