Diaphanosoma dubia is one of the dominant species in most tropical reservoirs, however, how it becomes dominant and whether food concentration plays a key role are unclear. In order to study the effects of algal food concentration on the growth and reproduction of D. dubia and to understand the possible causes for this small animal to be one of the dominant species in the tropical water bodies, the animals were fed by Chlorella pyrenoidosa as food with five organic carbon concentrations: 0.05mg/L, 0.1mg/L, 0.3mg/L, 0.6mg/L and 1.0mg/L, respectively. The survival rate was quite low and no reproduction at the food concentration of 0.05mg/L. The somatic growth rate and longest body length increased with the organic carbon concentrations of Chlorella pyrenoidosa, the longest body length was 1.087mm, 1.125mm, 1.225mm and 1.313mm, respectively. Food concentration showed no significant effect on embryonic and juvenile development periods, lifespan and the number of the cumulative eggs for each adult. The size at maturity and the mean number of eggs per brood both increased with the increasing organic carbon concentrations of Chlorella pyrenoidosa, but the duration of reproduction decreased. The intrinsic rate of increase increased with the increasing organic carbon concentrations of Chlorella pyrenoidosa. The net reproduction rate and the intrinsic rate of increase showed peak values at the food concentration of 0.6mg/L. Under the maximal food concentration of 1.0mg/L, the generation time was shortest and the intrinsic rate of increase was closed to the peak value. The proper concentrations for the growth of D. dubia were 0.6mg/L and 1.0mg/L. The D. dubia is smaller than many species in cladocerans such as Daphnia galeata and has lower number of eggs per female. Its small body size and few eggs seems not be caused by low food concentration. The maximal sized animals cultured in the high food concentration is close to the animals found in natural water bodies, this means that predation doesn't significantly reduce its body size. Small size, transparent body and quickly moving enhance its advantages to dominate in tropical water bodies.