Abstract: Artemia were reared, under zero water exchange, on four different microalgae feeding regimes: standard ad libitum feeding (SF1), half of SF1 (SF1/2), one third of SF1 (SF1/3), and a quarter of SF1 (SF1/4). In additional treatments, for each of these feeding regimes nitrogen waste from Artemia in the cultures was converted into bacterial biomass by addition of carbohydrate to produce carbon/nitrogen (C/N) ratio 10. The objective was to investigate what the contribution of bacteria to the Artemia diet was at different degressive algae feeding rations. After 15 days of culture period, the results of survival and biomass production (WW g/L) indicated that stimulating bacterial growth increased survival and biomass production of Artemia in all feeding rations when compared to the corresponding control treatments with algae only. Particularly, manipulating the C/N ratio in the SF1/3 treatment induced the improvement of Artemia biomass production equal to that obtained in the treatment where Artemia were offered solely algae at SF1 ration. Moreover, the results of fatty acid assimilation and especially 15N accumulation in Artemia indicated that Artemia utilized relatively more bacteria for the treatments with the lowest algae supply. These findings open perspectives for using bacteria to substitute or supplement microalgae in Artemia biomass production.