In this study, bettas raised in a physically complicated and social environment were in comparison with fish that were relocated to a poor and isolated atmosphere at the juvenile or subadult stage. The aggressive behaviors of the fish were evaluated at the juvenile, subadult, and adult stages. The mirror image test was used to evaluate competitive conduct. Although this test has limited predictive value for aggression directed at real rivals , it was specific because, unlike other behavioral tests, it does not have an effect on the concentrations of sex steroid hormones . Body parameters and plasma concentrations of steroid hormones were measured to compare the condition of the fish. The concentrations of estradiol E2 in females and 11 ketotestosterone 11 KT in males were measured to compare sexual maturity, and the cortisol awareness was measured to compare the tension response after the mirror image test.