This study was aimed to explore differences between day and night feeding of farmed European eels (Anguilla anguilla) on: (1) the growth and feeding behaviour of eels; and (2) the subsequent impact on the quality of the culture water. A 30 day field experiment was conducted in which 40 European eels (186.4 ± 9.26 g) were arbitrarily allocated into two replicate concrete ponds (200 x 100 x 125cm) that were divided into two treatment groups, one receiving feed by day (DF) and the other receiving feed at night (NF). Results revealed a significant improvement in eel's growth performance (larger final weight and faster growth) of the fish that were fed by night (NF). Moreover, feeding behaviour was also improved in the NF group with a significantly shorter latency to start feeding and shorter feeding duration. As a consequence of improved feeding behaviour, more favourable water quality conditions (higher dissolved oxygen concentrations and lower ammonia concentrations) were observed in the NF group. In conclusion, feeding eels by night could considerably enhance the culturing of eels by promoting enhanced growth and feeding behavior, and simultaneously improving water quality.

This study evaluated how water temperature (26, 28, and 30°C), number of meals per day (one or two meals), and protein percent in diet (20, 25 and 30%) impact growth performance, biometric indices, and feeding behavior of Nile tilapia, Oreochromis niloticus. Fish were randomly allocated into 18 equal replicate groups. Higher final body weight was observed in fish reared at 30°C and fed one meal per day containing 30% crude protein. Better weight gain, weight gain %, feed conversion ratio, specific growth rate, and condition factor were recorded in fish reared at 26°C and fed one meal per day containing 30% protein. The best length weight relationship was obtained in fish reared at 26°C and fed one meal per day containing 30% crude protein. Shorter feeding duration and duration of appetite inhibition latency were recorded in fish reared at 30°C, fed one meal per day, and given a diet containing 30% protein. The highest proactivity was recorded in fish reared at 30°C, received one meal per day, and with 25% crude protein in their diet. Conclusively, rearing Nile tilapia at 26–30°C with a lower feeding frequency (one meal/day) and a 30% crude protein diet achieved better performance and feeding behavior.