The Instituto de Acuicultura Torre de la Sal (IATS), one of the 120 institutes of the Spanish National Research Council (CSIC), is devoted to aquaculture research in areas including Nutrition, Reproduction and Health, among others. The scientists Óscar Monroig, Juan C. Navarro, Francisco Hontoria and Alberto Ribes-Navarro, of the Live Preys in Aquaculture, Larviculture and Ecotoxicoloy Research Group at IATS-CSIC, contribute to SIDESTREAM by providing expertise in the molecular mechanisms underlying the endogenous production of long-chain polyunsaturated fatty acids (LC-PUFAs) in marine invertebrates. Central to SIDESTREAM, IATS-CSIC team has demonstrated that multiple aquatic invertebrates have the capacity for de novo biosynthesis of the sought-after omega-3 LC-PUFAs (Kabeya et al 2018; Sci. Adv. eaar6849). This discovery highlights the importance of aquatic invertebrates as novel sources of omega-3 LC-PUFA for use in aquaculture and, among invertebrate phyla with such an outstanding metabolic capacity, SIDESTREAM focuses on low trophic level crustaceans and polychaetes. More importantly, culture of these invertebrates combining an adequate supply of LC-PUFA biosynthetic precursors available in sidestreams from bio-industries and optimized physical-chemical conditions enhancing LC-PUFA production pathways, emerges as a highly innovative and promising strategy to produce nutritious and sustainably sourced ingredients for aquaculture. Such a strategy is at the basis of SIDESTREAM, particularly the WP1 (Biomass Production) lead by IATS-CSIC. Briefly, WP1 consists of production of biomass from marine invertebrates (polychaetes and gammarids) and astaxanthin-producing bacteria. Optimization of culture conditions for both invertebrates and bacteria will be carried out in order to simultaneously enhance the output and nutritional quality of biomasses before these are utilized in WP2 (Processing). IATS-CSIC team coordinates institutions responsible for biomass production, generating the biochemical and molecular information that allow culture conditions to be optimized before being up-scaled for mass production required for feeding trials on commercially relevant fish and crustaceans (WP3).