This study aims to determine the relationship between water fertility and phytoplankton around floating net cages in Tomok Village, Samosir Regency. The study was conducted from July to August 2025 in the waters of Lake Tomok Village, Samosir Regency. Collecting sample at three stations: Station 1 with more floating net cages, Station 2 with fewer floating net cages, and Station 3 at a location…