ABSTRACT This study conducted in February-March 2019 at Marine Science Biotechnology and Marine Microbiology Laboratorium, Faculty of Fisheries and Marine, Riau University, Pekanbaru. The aim of this study is to know the effect of using heterotrophic bacteria to red nile tilapia’s (O. nilloticus) growth and to know the amount of heterotrophic bacteria in a pool. The study uses experiment…