Plants belonging to the Clusiaceae species are Garcinia mangostana Linn (mangosteen fruit). The skin layer of this fruit has been used as a traditional medicine for wound healing, topical infections. Mangosteen rind contains compounds including mangostin, mangostenol, mangostinon A, mangostenon B, trapezifolixanthone, tovofillin B, alpha mangostin, beta mangostin, garsinon B, mangostanol, flavonoids, epicatechin. Gartanin, gamma mangostin, garsinon E, epicatechin. Farming African catfish (Clarias Gariepinus) when facing serious problems such as fish are susceptible to disease, mainly due to bacteria. One type of bacteria that causes the disease is Aeromonas hydrophila. This type of bacteria can cause high fish mortality in African catfish (Clarias Gariepinus) of various sizes. The purpose of this study was to determine the effect of mangosteen rind extraction on the growth of Aeromonas hydrophila bacteria in vitro, as well as the 96-hour Lethal Dose (LD50) value of mangosteen rind extract after exposure to African catfish (Clarias Gariepinus). In this study, the antibacterial activity of the material was tested in vitro with concentrations of 0%, 1.56%, 3.125%, 6.25%, 12.5%, 25% and 50%.