Eurytemora affinis was collected on two occasions in February and March 1981 in the Schlei Fjord, FRG, and subsequently kept in the laboratory for experiments which were conducted through April. Ingestion, assimilation and respiration of E. affinis fed with the green alga Nannochloris sp. were measured at an experimental temperature of 15°C and a salinity of 12‰. The aim was to outline a carbon budget for use in aquaculture projects. The weightspecific ingestion rate increased with increasing food concentration following an Ivlev curve; it suggests an upper food threshold of 2.12 μg C μg body-C-1 d-1. The mean assimilation efficiency was 89%; it was independent of food uptake in the range investigated. The respiration rate ranged from 0.12 to 0.42 μl O2 copepod-1 h-1; the mean respiration rate was 0.25 μl O2 copepod-1 h-1, corresponding to 0.77 μg C μg body-C-1 d-1. The growth efficiency was calculated as a function of food uptake. At a daily ration of 42%, the gross growth efficiency was 0%; at a daily ration of 128%, it was 60%. It is predicted that copepods fed at a concentration of 340 μg Cl-1 will grow optimally.