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Nile tilapia (Oreochromis niloticus) is one of the most important cultured species worldwide. The research aims to clarify the feeding characteristics, such as daily feeding pattern of Nile tilapia using a self-feeding technique. The feeding pattern was conducted under two rearing conditions, indoor treatments under a controlled light regime (LD 12:12) and constant water temperature (25°C), and outdoor treatments under natural conditions which consisted of duplicate trials with two periods each. The outdoor treatment was carried out from early summer through late autumn in Mie, Central Japan. Daily self-feeding activity of Nile tilapia in indoor treatments was nearly daytime feeding pattern, synchronizing with the given photoperiod (24 hr). However, the self-feeding activity in the outdoor experiments from early summer to early autumn was almost daytime feeding pattern, but it became less clear and shifted to a nighttime feeding profile in late autumn. The results revealed that Nile tilapia has a dualistic capacity for demand-feeding both in light and dark phases. These results might have been caused by the seasonal change in light intensity and/or water temperature. Information obtained from the self-feeding experiments enables us to identify the influence of environmental changes on the physiological condition of farmed fish through their expression of appetite. K E Y W O R D S diel feeding behaviour, Nile tilapia, Oreochromis niloticus, self-feeding 1 | INTRODUCTION The Nile tilapia (Oreochromis niloticus, L.) is one of the most important aquaculture species groups especially in South East Asia, Africa, South America and China. Several species of tilapia are cultured commercially, but Nile tilapia is the predominant cultured speciesand its global production has reached to nearly 3,670,000 tons in 2014 (FAO 2017). The gross production of Nile tilapia increases year by year because of the strong worldwide demands for this potential freshwater fish as a food resource of human being. Therefore, further research is necessary for the establishment of the culture technology for this species because knowledge about the physiology and ecology on this fish species is still lacking and there are many obscure points such as appropriate rearing conditions and feeding technology.The self-feeding system delivers food based on the learning ability of fish and it is considered to be a feeding technique for aquaculture that might be controlled by a biological clock (Alan€ ar€ a, 1992) with food demands depending on appetite (Amano et al., 2007). Therefore, the feeding method agrees with the physical state of the cultured fish. Indeed, self-feeding systems have been studied in several culture fish species such as rainbow trout Oncorhynchus mykiss (

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Tilapia have high resistance to various diseases, tolerance to low and high temperatures, efficiency in feed and fast growth, recently growing in saline water with salinity up to 20 ppt. The addition of Sargassum extract into the feed is an alternative to maintain water quality and digestibility of feed in the fish body. Sargassum sp, has a fairly complete nutritional content, it can certainly have a growth effect when added to fish feed, according to previous research. The nutritional content of Sargassum sp. including crude protein content 5.19%, ash content 36.93%, fat 1.63%. Sargassum sp. has a protein content of 7.94%, fat 0.72%, ash content 35.84%, crude fiber 4.93%, and carbohydrates 50.57%. Based on the background, it is necessary to do research on the addition of the enzymatic extract of Sargassum sp. such as neutrase and viscozyme into feed on feed conversion and growth performance of tilapia (Oreochromis niloticus). Sargassum collected from Pantai Karapyak, Pangandaran, West Java, Indonesia. Material and methods that used in research ranging from preparation of Sargassum extract, preparation of experimental animal, and experimental design. The utilization of Sargassum extract were effective to increase Feed Consumption (FC), Feed Utilization Efficiency (FE), and Absolute Growth Performance (AG) with the result of significant difference (p< 0.05) in FE and AG results. The highest result in all parameters were occurred in treatment fed by 2 g/Kg enzymatic extract of Sargassum (viscozyme).