Appropriate rearing conditions for successful farming of white sea bream Diplodus sargus L. have not yet been studied in depth, while one of the major problems is the species increased aggressiveness. Given the known e¡ect of density and background colour on ¢sh growth, welfare and social behaviour, the present study aimed to investigate whether the two factors combined could favour D. sargus performance. Juveniles (17.37 AE 0.06 g) were reared in white, light blue and black tanks under low (7 ¢shtank À1 or 1.96 kg m À 3 ) and high (28 ¢sh tank À1 or 7.79 kg m À 3 ) density for 87 days. Water quality was not a¡ected by experimental treatments. The best overall performance (growth, food utilization, body protein content, liver fatty acids) was achieved under low density and white or light blue tanks. Increased incidence of social interactions was indicated in ¢sh under high density or when reared in light blue and black tanks. The present results clearly suggested that the use of black tanks should be avoided. On the other hand, stocking D. sargus at a density of up to 7.79 kg m À 3 may be feasible because productivity was greater even if growth was slower. In this case, however, the use of white tanks is highly recommended.