Respiration data for different stages of Brachionus calyciflorus, fed with three concentrations of Kirchnerielia lunaris at 20°C, are presented. Increasing oxygen consumption from 4.1 to 4.6. 10−3 μl/h x ind. with food decreasing from 5.106 to 106 and 4.105 cells/ml has been found for adult females with one egg, but other age groups showed divergent results. Based on the respiration data for age groups 0 to 12 and 12 to 24 h old and some other results and calculations-e.g. dry weight and caloric content of eggs and females, ingestion rates/h for the different concentrations of food — energy budgets for juvenile, growing B. calyciflorus are presented.