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The cryptophyte Rhodomonas salina is widely used as feed for copepod cultures. However, culturing conditions to obtain high-quality algae have not yet been efficiently optimized. Therefore, we aimed to develop a cultivation protocol for R. salina to optimize its nutritional value and provide technical recommendations for later large-scale production in algal photobioreactors. We studied photosynthesis, growth, pigments, fatty acid (FA) and free amino acid (FAA) composition of R. salina cultured at different irradiances (10-300 μmol photons m −2 s −1 ) and nutrient availability (deficiency and excess). The optimal range of irradiance for photosynthesis and growth was 60-100 μmol photons m −2 s −1 . The content of chlorophylls a and c decreased with increasing irradiance while phycoerythrin peaked at irradiances of 40-100 μmol photons m −2 s −1 . The total FA content was maximal at optimal irradiances for growth, especially under nutrient deficiency. However, highly unsaturated fatty acids, desired components for copepods, were higher under nutrient excess. The total FAA content was highest at limiting irradiances (10-40 μmol photons m −2 s −1 ) but a better composition with a higher fraction of essential amino acids was obtained at saturated irradiances (60-140 μmol photons m −2 s −1 ). These results demonstrate that quality and quantity of FA and FAA of R. salina can be optimized by manipulating the irradiance and nutrient conditions. We suggest that R. salina should be cultivated in a range of irradiance 60-100 μmol photons m −2 s −1 and nutrient excess to obtain algae with high production and a balanced biochemical composition as feed for copepods.

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To determine the optimal food concentrations for the mass culture of the tropical copepod Pseudodiaptomus annandalei at relevant temperatures, we conducted three functional response experiments. In these experiments, we quantified the grazing rate via the faecal pellet production of adult males and females. They were fed for 6 hr on one of three commonly used microalgal species in aquaculture: Chaetoceros muelleri, Isochrysis galbana and Tetraselmis chui at concentrations of 12.5–3,200 μg C L−1 and three temperatures 25, 30 and 35°C. The number of pellets (PP) and the total volume of pellets (SPP) of both sexes increased rapidly with the increase in the microalgal concentrations until maximal pellet production (PPmax or SPPmax) was obtained, where females showed a consistently higher SPP than males. This pattern was similar for all three microalgal species. Males showed inconsistent PP and SPP in response to algae and temperatures. For females, they showed two clear patterns: a higher PP and SPP with increasing temperature from 25 to 30°C, then a lower PP and SPP at 35°C. Our study provides fundamental knowledge of pellet production to determine the food requirements of P. annandalei under different temperatures that are essential for designing the technical protocol for biomass culture.