Aquaculture is one of the main sources of livelihood of the state of Assam in the northeast of India. In this study, Cachar district of Assam has been selected to study and assess the impact of various sizes of fish farm on the economic condition of farmers. The study was conducted in the villages of 5 blocks namely Borjalenga, Tapang, Narsingpur, Sonai and Palonghat with an objective to suggest optimum size of the pond and analyze the production rate of different type of fish farm. The data was collected from around 169 farmers by the principle of participatory rural appraisal a method used by nongovernmental organizations. Most of the farmers are not much educated and most of them lived below poverty line. The number of medium size ponds (0.5 to 1 hectare), and small farm ponds (between 0.3 to 0.5 hectare) are highest followed by very small (less than 0.3 hectare) and then large size ponds (more than 1 hectare). In the study area, both excavated and embankment type pond exist. The results indicate that even with possession of small and medium size fish farms, better annual production rate of fish can be achieved by better management practices. 83% of all fish farms in Cachar district are very small, small or medium size fish farms. Only 17% of the farms are of large size. The annual production is remarkably good for small and medium size farms. The results indicate that small and medium farm sizes have better annual production rate than other farms. Thus, small to medium farms are economically more viable for the Cachar district. Highlights • Cachar district has been selected for optimal study of fish pond. • The study is based on socioeconomic condition of fish farmers. • The fish farm has been divided in small, medium and large size ponds. • The results reveal that small to medium size ponds is optimal pond size.