A series of experiments of each 25 days were conducted to evaluate the suitability of four microalgal diets for the culture of the tropical cyclopoid copepod Oithona similis. The mono-algal diets were Chaetoceros calcitrans, Isochrysis galbana, Chlorella marina and Nannochloropsis oculata. Present work was carried out in a Completely Randomized Design (CRD) with four treatments and three replicates. After feeding O. similis with the 4 algal diets for 25 days, population density of adults, copepodites, nauplii and egg bearers were determined. Density and population growth rate of all stages were the maximum when fed with C. calcitrans and it was confirmed as an excellent diet for O. similis. Growth performance as indicated by population density and growth rate was significantly (P<0.05) higher for all stages when fed with C. calcitrans compared to the rest of the diets. The biochemical profile of O. similis showed superiority in protein (55.6%), and lipid (33.4%) contents on feeding with C. calcitrans. Since the strain is cultivable with good nutritional profile and high survival rate, it gives an immense scope of high value larval feed for use in marine hatcheries. Based on the current results, it is suggested that among the diets tested, the diatom C.calcitrans was the best for enhanced production of all stages of O. similis in controlled conditions followed by I. galbana

Tropical copepods, Oithona similis, growth rate, density, nutritional profile