The use of artificial substrates (polyethylene screens) was investigated during the nursery rearing of the pink shrimp Farfantepenaeus paulensis cultured in fixed cages installed in a shallow estuarine inlet of the Patos Lagoon, southern Brazil. High water renewal rates during the experimental period kept water quality in the suitable range for penaeid shrimp culture. Although shrimp were fed a high quality artificial diet (40% protein) throughout the experiment, they were observed to occupy the substrates and actively graze on the biofilm. The bulk of the biofilm was composed of diatoms, filamentous cyanobacteria, protozoa and nematodes. Biofilm chlorophyll a concentration was significantly affected by shrimp grazing pressure and the composition of the diatom community suffered significant changes after shrimp introduction to the cages. At the end of the trial shrimp reared in the presence of artificial substrates achieved significant higher survival, growth and total biomass (p < 0.05). Biofilm was likely an additional source of food for the reared animals.