Harmful algae blooms plague aquatic ecosystems around the world. They impact water quality and ecosystem diversity, cause dead zones, and cost the fishing and tourism industries millions of dollars. In this project, different genotypes of Daphnia magna were compared for algae consumption. The most effective genotype was then tested under different environmental conditions to see which factors helped or hindered their success at harmful algae bloom treatment and prevention. It was determined that genotype 4 is the ideal genotype of D. magna to biomanipulate to treat and prevent harmful algae blooms, they can effectively do this in nutrient and plastic polluted environments, and their health and success can be improved with calcium carbonate and naturally occurring aquatic microbes.