siamese fighting fish sickA complicated environment decreased aggression or even led to cohabitation without combating in intruder–resident tests with the pearl cichlid Geophagus brasiliensis , while other cichlid species showed contrary results . In male bettas that are socially isolated at 6 weeks after hatching, the occurrence of agonistic behaviors raises after the termination of mutual fights . Under average rearing circumstances, whether in non-public aquariums or in commercial facilities, male bettas become distinguishable from women at 2 to 4 month after hatching and must be separated into particular person bins to circumvent accidents due to aggression . Females bettas are generally reared in communal tanks, even though, some women folk have been pronounced to exhibit fierce aggressiveness . Furthermore, it has been documented that a stable group of males and females may be based if adequate space is accessible . We hypothesized that the rearing condition impacts the aggression level of bettas.