Thanks to a major breakthrough in the search for sustainable tuna feed, we are now a step closer to the possibility of environmentally sound tuna farming. Closed cycle tuna aquaculture, from hatch to harvest, combined with sustainable formulated grow out diets offer the best opportunity we have to prevent the depletion of wild tuna stocks while supplying the global market demand for these species. Recent research by Ichthus Unlimited, LLC, funded by the Illinois Soybean Association checkoff program, produced various soy-based diets for larval Atlantic Bluefin tuna in Spain and for juvenile yellowfin tuna in land-based facilities in Panama. Building on these experiences, a diet was successfully tested on ranched Pacific Bluefin tuna in oceanic net pens off the northwest coast of Mexico. Bluefin are normally fed wild-caught sardines while they are grown/fattened to market size, with an approximate feed conversion ratio (FCR) of 28:1. The new formulated diet decreases the FCR to 4:1. The novel diet is avidly consumed, nutritionally complete, sustainable, economical, and scalable. This breakthrough is a significant step towards closed cycle cultivation of tuna species, which will ease pressure on threatened wild tuna populations. For more information, contact feedingtuna@ilsoy.org.