Lake Mahalona is one of the lakes located in the Malili Complex, South Sulawesi and is included in the Natural Tourism Park Area. Cichlasoma trimaculatum are ornamental fish from the Cichlidae family that become invasive in Lake Mahalona. A total of 29 fish species were recorded in this lake, and most of them are endemic fish. It is estimated that native and endemic fish species and populations will decline due to invasive alien species intentionally or unintentionally in Lake Mahalona. The study to determine the size distribution and length-weight relationship of C. trimaculatum was conducted in Mahalona Lake. The study was conducted at 11 stations in October 2020. Experimental gill nets used to catch Bilih. The total length of C. trimaculatum ranged from 10.0 ± 1.57 cm (Kusapa and Badilla stations) to 18.0 ± 1.57 cm (Benu station), and the weight ranged from 19.0 ± 19.2 g (Kusapa station) to 140.0 ± 19.2 g (Muara station). The correlation coefficient (r) value for this fish ranges from 0.8685 - 0.9691. The growth pattern of C. trimaculatum was a negative allometric characteristic. An exception in Muara dan Tandu Mata stations was positive allometric.