Abstract: Copper sulfate complex was appiled as algaecide for emergency control of algae bloom in eutrophicated ponds.Effects of the application on water quality and Cu enrichment in Tilapia sp. were studied.Results show that algae bloom was effectively put under control after the application,with chlorophyll a concentration falling from 298.98 to 40.71 μg·L^-1 and turbidity from 14.45 to 5.70 NTU simultaneously.During the period of the treatment,the concentration of copper ions in water was lower than 0.3 mg·L^-1 ;Ten days after the treatment,the algae began to in crease in biomass,bringing up chlorophyll a concentration from 40.71 to 125.29 μg·L^-1 and turbidity from 5.70 to 12.15 NTU,and 22 days after the treatment,Cu²⁺ concentration in the water fell below the detetable limit.Various organs of Tilapia sp. followed the order:liver(512.50 mg·L^-1 )>gill(17.00 mg·L^-1 )>muscle in Cu enrichment ability.No obvious Cu accumulation was found in fish meat.In addition after the treatment,Cu accumulation in gills of the fish declined significantly.