Goldfish Carassius auratus were maintained on a 12L:12D (12-hour-light:12-hour-dark) photoperiod at 14 C and fed 1% of body weight once daily for 3 weeks. The fish had differences in growth depending on the feeding time relative to the light-dark cycle: Fish fed 18 hours after light onset (6 hours into darkness) grew more than others. Common carp Cyprinus carpio were maintained on a 16L:8D photoperiod at 15 C and fed 2% of body weight at one of six feeding times for 5 months. There were no consistent growth differences among treatments, nor any apparent debilitating effects of long-term enforced feeding times on common carp. The feeding time most conducive to body-weight gain appears to vary with the season and among cultured fish species. Timing the daily meal may be a valuable tool for aquaculture.