This study aims to determine the benefits and optimal concentration of ketepeng cina leaves (Cassia alata L.) ethanol extract prevent A. japonicus infestation in gourami fish. research was conducted May - August 2019. The method used is experimental method. design Complete by Randomized Design (CRD ) with four i.e. Control (P0), 209 ppm (P1), 418 (P2), 627 (P3). Data analyzed using Analysis Var...