This Small Business Innovation Research Phase I research aims to evaluate a range of natural substances as feed additives or passive dip solutions in an in-cage dip device. Individually, or in combination, these novel methods may help control ectoparasites in offshore fish farms. Recent development of commercial-scale hatchery production techniques for high-value marine fish offers tremendous opportunity for expansion of open ocean aquaculture. Control of ectoparasites in farmed fish remains a concern, of both environmental and economic significance. Parasites from wild fish can proliferate among cultured stocks, affecting the economic viability of the farm, and amplifying disease prevalence in wild fish. Inshore farms overseas often rely on bath treatments to control parasites. However, prolonged bath treatments are not practical in most open ocean farm conditions, and many effective compounds are not permitted for use in the U.S. Natural feed additives may reduce infections. Fish might also be conditioned to expose themselves to treatments to control ectoparasites. This project tests a range of natural substances as feed additives or passive dip solutions. A passive dip device will be tank-tested. Individually, or in combination, these novel methods may help control ectoparasites in offshore fish farms. The broader impact will be to address the US government's aspiration to increase aquaculture production five fold by 2025. The need is pressing: the seafood trade deficit is almost $8 billion, and domestic seafood demand is increasing. Capture fisheries face declining stocks, closures, and increasing regulation. Open ocean aquaculture presents the best opportunity for meeting this national priority and the world's seafood protein needs in a sustainable, environmentally-sound manner. Offshore farms can produce high-value marine fish without significant impacts on water quality, benthic habitats or other ocean user groups.