This study was carried out on Nile tilapia at Fish management and Behaviour Research Unit, Department of Veterinary Public Health, Faculty of Veterinary Medicine, Zagazig University. Three experiments were designed to investigate the effect of stocking density, water temperature of aquaria and feeding regime on the behaviour and performance of Nile Tilapia. During the period from November (2018) till the end of December (2019). I- The effect of stocking density on behaviour, performance of Nile Tilapia and water quality. In this experiment, 240 with 30 gram weight, apparently healthy Nile Tilapia fingerlings were divided into four duplicated aquaria under four different rearing stocking density (15, 25, 35, and 45) fish were weighted individually every 14 days till the end of experiment to determine the growth rate parameters and study the effect of different stocking density on behaviour, performance of Nile Tilapia and water quality. 1- There was a very high significant effect of stocking density on mean frequency and duration (sec) of feeding behaviour during weeks of experiment in groups (3 - 4) in compare with group (1) control. 2- There was a very high significant effect of stocking density on mean frequency and duration (sec) of foraging behaviour during weeks of experiment in groups (3 - 4) in compare with group (1) control. 3- Frequency and duration of surfacing behaviour were significantly higher at high stocking densities specially group (4) in compare with group (1) control. 4- Frequency and duration of surface swimming behaviour were significantly affected by stocking density, since it was the greatest in groups with high stocking densities than other groups. 5- Stocking density significantly affected frequency and duration of both middle and bottom swimming behaviour among groups as low and medium stocking densities showed the highest means than high stocking densities. 6- Body care behaviour (shaking behaviour and scratching behaviour frequency and duration) was significantly higher in groups (3 - 4) than groups (1-2). 7- There was a very high significant effect of stocking density on mean frequency and duration (sec) of aggressive behaviour during 10 weeks of experiment in groups (3 - 4) in compare with group (1) control. 8- Frequency of mid line crossing test was significantly affected by stocking density as it was the highest in group (1) control in compare with other groups. 9- Stocking density significantly affected frequency of laterality as it was the highest in group (4) than groups (2-3) but it wasn't occurred in group (1). 10 - There were significant difference in average live body weight throughout weeks of experiment, it was higher in group (1) control than other groups. 11- The average body weight gain, average daily gain, specific growth rate and feed conversion ratio were significantly affected by different stocking densities throughout weeks of experiment as group (1) control was the highest in compare with groups (3-4). 12- High stocking densities cause morbidity and mortality as in group 3 and 4 while no mortality and morbidity in low and medium stocking densities. 13- Stocking density negatively affected on the health, where groups with high stocking densities showed hyper pigmentation, cyanosed gills, fin erosion, bulged eye and detached scales. 14- Stocking density affected water parameters where high stocking densities had low oxygen and water pH levels, increased ammonia and nitrite levels and increased carbon dioxide exposure comparing to low and medium stocking densities. II- The influence of water temperature of aquaria on behaviour and performance of Nile Tilapia. Studying the effect of different water temperature (20, 24, 28, 32 ºC) on behaviour and performance of Nile Tilapia. The obtained results were as the following: 1- Frequency and duration of feeding behaviour were significantly affected by water temperature of aquaria as it was higher in group 3 (28 ºC) than other groups. 2- Foraging behaviour of Nile tilapia was higher in group 3 (28 ºC) than other groups, but the difference had no significant effect. 3- Frequency and duration of surfacing behaviour were significantly higher at group 4 (32ºC) in compare with other groups. 4- Frequency and duration of surface swimming behaviour were significantly affected by water temperature, as it was the highest in group 4 (32ºC) than other groups. 5- Middle and bottom swimming behaviour frequency and duration were significantly higher in group 3 (28 ºC) and group 1 (20 ºC) respectively than other groups. 6- Body care behaviour (shaking behaviour and scratching behaviour frequency and duration) was significantly higher in high water temperature as in group 4 (32ºC) in compare with other groups. 7- There was a very high significant effect of water temperature of aquaria on mean frequency and duration (sec) of aggressive behaviour during weeks of experiment in group (4) in compare with other groups. 8- Frequency of mid line crossing test was significantly affected by water temperature of aquaria, group (3) showed the highest mean frequency of crossing test while the lowest in group (1). 9-There were significant difference among groups in average live body weight throughout weeks of experiment, it was higher in group (3) than other groups. 10- The average body weight gain, average daily gain, specific growth rate and feed conversion ratio were significantly affected by different water temperature of aquaria throughout weeks of experiment as group (3) was the highest in compare with other groups. 11- Low water temperature caused morbidity and mortality as in group (1) while no mortality or morbidity in other groups. III- The impact of feeding regime on performance and behaviour of Nile Tilapia. In this experiment, the effect of different feeding frequency (one, two, three times) at different time (group1 at (9am-11am-1pm), group 2 at (9am-11am), group 3 at (9am-1pm), group 4 at (11am-1pm), and group 5 at (9am) on Nile tilapia behaviour and performance. The obtained results were as the following: 1- Frequency and duration of feeding behaviour were higher in group (1) than other groups, but the difference had no significant effect. 2- There was no significant effect of feeding frequency on mean frequency and duration (sec) of foraging behaviour during weeks of experiment but it was higher in group (1) than other groups. 3- Feeding frequency significantly affected frequency and duration of surfacing behaviour, it was higher at group (5) than other groups. 4- There was a very high significant effect of feeding frequency on mean frequency and duration (sec) of surface swimming behaviour during weeks of experiment in group (5) in compare with other groups. 5- Frequency and duration of middle and bottom swimming behaviour were significantly higher in group (1) in compare with other groups. 6- Body care behaviour (shaking behaviour and scratching behaviour frequency and duration) was significantly differed among groups, as it was higher in group (5) than other groups. 7- Feeding frequency significantly affected frequency and duration of aggressive behaviour, it was higher at both groups (2-3) in frequency while group (5) in duration. 8- There were no significant difference among groups in average live body weight throughout weeks of experiment, but group (1) was the highest than other groups. 9- The average body weight gain, average daily gain, specific growth rate and feed conversion ratio were not significantly affected by different feeding frequency throughout weeks of experiment, but group (3) was the highest in compare with other groups. Recommendation 1- Stocking density is an essential factor used in aquaculture industry for high growth and welfare with total fish harvest in ponds. 2- Water temperature must be taken into consideration due to its great impact on Nile tilapia growth and welfare for achieving maximum productivity and profitability. 3- Increasing feeding frequency accelerates growth and helps Nile tilapia in practicing all their behavioural activities efficiently with high body weight.