Fish health is critical to aquaculture production. Health impacts the ability to complete the production cycle in a predictable manner, market a high-quality product, and ultimately generate the greatest possible revenue. Sick and stressed fish do not eat to their full capacity, which means they do not grow at their optimal rate. When this occurs, the fish may have an appearance that is not acceptable to consumers, such as skin lesions. Fish that do not grow cost the farmer time and money in labor, feed, and other resources. The farmer must provide the optimal environmental conditions for the fish to grow so that they remain healthy and achieve their full potential. This publication will cover concepts that affect fish health such as how to identify and prevent diseases, how to treat issues as they arise, and the regulatory aspects of treating and transporting fish.