With the development of the aquatic feed industry, new feedstuff and feed additives have been developed, but their roles on the growth and immunity of different aquaculture animals remain to be examined. In addition to essential nutrients, feedstuffs and feed additives must contain some biologically active constituents to support fish growth and wellness. However, some also have adverse effects on growth performance through the introduction of undesirable materials. This Special Issue focuses on the application of feedstuffs and additives in aquaculture species' growth and immunity, especially recently developed feedstuff and additives.