FEEDNETICS 4.0 aims to improve the previous versions of FEEDNETICS, a software for predicting the growth, biochemical composition, and waste outputs of European seabass, Atlantic salmon, Gilthead seabream, Rainbow trout, and Nile tilapia fed different diet compositions and quantities at several temperatures. This improved user-friendly decision-support tool will comprise: (i) a fish farmer version, designed to help planning and managing fish feeding by optimizing the composition and proportion of feed ingredients and water temperature; and (ii) a feed formulator version, designed to help develop new feed formulations based on fish growth and body composition, feed cost, and waste outputs.