We investigated the fungicidal effects of sodium hypochlorite solution (a food additive) on Saprolegnia parasitica, a well known pathogen causing saprolegniasis in freshwater fishes. The effects were measured by zoospore germination inhibition and mycelial growth inhibition of the pathogen. Zoospore germination was completely inhibited by a 10 second treatment at the residual chlorine concentration of 2.5mg/l. Mycelial growth was also completely inhibited by a 60 minute treatment at 20mg/l. These results indicate that the sodium hypochlorite solution has strong fungicidal activity against S. parasitica.
