"Studies on the molting cycle of Macrobrachium tenellum are not available, which limits the scope of studies of growth and reproduction. The duration of the molt cycle was determined under controlled experimental conditions. The prawns were divided into four groups according to weight: Group 1 (1.0–1.9 g), Group 2 (2.0–2.9 g), Group 3 (3.0–3.9 g), and Group 4 (4.0–9.0 g). The increase in total weight was higher in groups 2 (23.4%) and 3 (20.3%) than in group 1 (~18%) and 4 (~18%). The increase in size after molting among all groups was statistically different: in group 1 it increased 6.1% (highest) and in group 2 it increased 2.2% (lowest). The duration of a complete cycle was 8.9, 9.4, 10.4, and 15.1 days for groups 1, 2, 3, and 4, respectively. The lengths of the molting cycles were not significantly different between groups 1 and 2, but group 4 was different from group 1."