ABSTRACTWater stable, uniformly14C radiolabeled, chemotactically‐active bacteria‐laden, artificial detritus was formulated by a rapid, simple method and used to follow the assimilation of bacterial macrommolecules into the foregut, midgut and tail tissue of aquarium‐acclimated freshwater prawns,Macrobrachium rosenbergii(de Man) in time course experiments under conditions of starvation, heavy supplemental feeding and sudden crowding. Over a 24‐hour time course with starved prawns, the proportion of the label assimilated into lipid in the midgut and tail tissue increased 12.3% and 8.0%, respectively, with decreased proportions of the label in carbohydrate in the midgut and protein in the tail tissue. Starved prawns incorporated similar proportions of the label in carbohydrate and protein of the midgut as did heavily fed prawns but shunted a larger proportion of the label into lipid. Protein was catabolized in order to synthesize lipid and appeared to be used as an energy source. Suddenly crowded prawns greatly elevated the amount of radioactivity proportioned into carbohydrates and lipids of the midgut at the expense of greatly lowered protein activities.The formulation prepared here, which appears chemotactically and visually active as artificial “fish feces,” may have wide applicability in many aquaculture pond ecology and nutrit