This investigation was devoted to the study of the possibility of using microalgae Acutodesmus dimorphus (Turpin) Tsarenko as a fodder organism for Daphnia growing. It was proposed to use as a nutrient medium for algae waste water from RAS (Recirculating Aquaculture System). Algae was cultivated for 21 days with a 16-hour photoperiod, illuminated with fluorescent lamps of 2500-4000 lux and at the temperature of 24 ± 2°C. A sufficiently high content of protein, lipids and carotenoids in A. dimorphus biomass has been established, which makes it possible to use it as a feed substrate for growing Daphnia. The amino acid profile of the algae biomass was analyzed. The dominant content of alanine, glutamic acid and leucine is established. There were approved two schemes of Daphnia cultivation, namely cocultivation with A. dimorphus and regular replenishment of Daphnia culture by A. dimorphus biomass. The rate of increase in the number of Daphnia individuals and their consumption of microalgae culture was analyzed. In the biomass of Daphnia obtained by joint cultivation with A. dimorphus algae, an increased content of lipids and carotenoids was established. The content of total proteins was not significantly different with both approved growth regimens. By the rate of increase in the number of Daphnia individuals and their nutritional profile, the scheme of co-cultivation was recognised as optimal.