The success of fish farming in cages depends entirely on the proper quality of the water around the cage, and the farmer must strive to minimize the environmental pressures on the fish. One of the important factors that create and intensify environmental pressures on cages is the presence of abundant nutrients that can pose risks such as dynamic changes in biological communities such as (phytoplankton, overgrowth of harmful species, and the possibility of non-native and invasive aquatic growth in the Caspian Sea.) and vice versa reduce or eliminate some species as well as algal bloom which can sometimes be dangerous for breeding, therefore, the study of phytoplankton communities and their interaction with fish farming is necessary and important. Therefore, in this study, in the area of the cage and around the cage based on the proposed methods were sampled and identified.