Fish meal is being increasingly substituted in diets for gilthead sea bream and Sea bream with ingredients of terrestrial origin. The replacement of Fish Meal (FM) and Fish Oil (FO), as main protein and lipid sources by alternative ingredients, may alter the micronutrient contents in the diets, leading to deficiencies or excess in several micronutrients related to fish growth, feed efficiency and health (Fountoulaki et al., 2016; Dominguez et al., 2019a, 2019b). Nowadays, aquafeeds for Mediterranean species are mostly based on nutritional requirements determined for other species (NRC, 2011) and in many most micronutrients, the requirements have not been yet determined for fish species. Hence, those feeds may be deficient or overdosed in some nutrients and, consequently, negatively affect KPIs (Dominguez et al., 2016). PerformFISH WP4 aimed to define the recommended levels for minerals and vitamins in gilthead sea bass and Sea bream diets to produce Species-­‐Specific Nutrient Balanced Formulations and improve KPIs in relation to growth, feed utilization and mortality in Mediterranean aquaculture. Despite there is scarce information published about nutrients requirements and availability for gilthead sea bream and sea bass (essential fatty acids, protein,…), certain national and EU funded projects produced some information about the recommended dietary levels for specific nutrients (phospholipids, Zn, Vit B5…). This critical nutritional information has been compiled and collected by PerformFISH and included in Milestone 4.1. Besides, since the nutritional requirements of some nutrients essential to improve KPIs have not been yet determined for gilthead sea bream and sea bass, PerformFISH has conducted a series of studies to determine the recommended dietary levels to produce Species-Specific Nutrient Balanced Formulations. In the case of gilthead sea bream, the trials were conducted to define the effect of fat-­‐soluble vitamins (A, K, and D), minerals (Cu, Mn and Se) and B group vitamins (B1, B9, and B12), whereas for Sea bass different profiles of chelated minerals have been tested. Deliverable 4.1 is mainly composed of the major experimental findings and, thus, the nutrient recommendations to define the threshold of nutritional quality for both fish species as keystone elements of the Mediterranean production.