The growth and health of aquaculture organisms are related to profit and cost. Probiotics are not only used in aquatic feeds to improve the growth and health but also in environments to maintain optimal culture conditions. This course covers but not limit to the following topics: 1) strategies for isolation, screening and identification of probiotics from variable habitats and aquatic hosts (fish and shellfish), 2) in vitro and in vivo functional activities evaluations, 3) mucosa immunity between probiotics and intestines and 4) the field trials.