"After 29 days without water exchanges, 55% of the total nitrogen (N) inputs were retained as shrimp biomass in 1 m3 cultures of juvenile Litopenaeus vannamei with artificial substrates (Aquamats®), in comparison to 37.2 to 44.8% without Aquamats. The N discharged with the effluent was 1.8-2.3% of the inputs, and the sediments contained 35.9-37.3% of the N inputs without Aquamats and 14.7 to 13.6% with Aquamats. In these, close to 16% of the N inputs were in the periphyton, indicating that additional substrates are an attractive alternative for nutrient recycling in shrimp farms operating as closed systems."