Dartmouth scientists have created a more sustainable feed for aquaculture by using a marine microalga co-product as a feed ingredient. The study is the first of its kind to evaluate replacing fishmeal with a co-product in feed designed specifically for Nile tilapia. The results are published in the open access journal, PLOS ONE. To address the environmental sustainability concerns regarding aquafeed, a Dartmouth team has been developing sustainable feeds for Nile tilapia, which examine the effectiveness of replacing fishmeal and fish oil with different types of marine microalgae. Marine microalgae are excellent sources of essential amino acids, minerals, vitamins, and omega-3 fatty acids, and can therefore, meet the nutrient requirements of fish. Omega-3 fatty acids are important for maintaining fish health; they also have neurological, cardiovascular and anti-cancer benefits to humans. The Dartmouth research team's latest work replaces fishmeal with a marine microalga co-product, Nannochloropsis oculata, which is rich in both protein and omega-3 fatty acids, including eicosapentaenoic acid, that are essential to fish growth and quality. The co-products are left-over algae meal, after the oils have been extracted from commercially-grown algae biomass to manufacture nutraceuticals, chemicals and fuel applications. The co-product is available at commercial scale and continued increases in supply are expected. The study's findings show promise in replacing conventional protein ingredients in tilapia feeds.