The objective of the research was to investigate the effecitivity of kalmegh leaf (Andrographis paniculata Ness) to bacterial infection (Aeromonas hydrophila) on common carp (Cyprinus carpio L). This research was conducted in laboratory of Parasite and Disease of Fish, Fisheries and Marine Science Faculty, Riau University from March until May 2009. Consentration ofkalmegh leaf extract in ea…