The presentation *Greenwater Microalgae: The Main Algal Aquafeed* discusses the significance of microalgae as a cost-effective and abundant source of cultured seafood biomass. It covers the standard costs with microalgae production compare to microalgae production in greenwater aquaculture, emphasizing its economic advantages. Utilizing FAO report data, the presentation highlights how greenwater polyculture not only feeds fish but also recycles their waste, leveraging sunlight for sustainable aquaculture practices. This approach underlines the role of microalgae in promoting environmentally friendly fish farming methods.