An in vitro evaluation of the effect of three fungicides on the growth rate (GR) of Fusarium solani and Fusarium semitectum was performed. The tested fungicides, commonly used in fish farming, were sodium chloride (NaCl), methanol-stabilised formaldehyde (F) and malachite green (MG). Both Fusarium species were isolated from eggs of the Argentinean pejerrey Odontesthes bonariensis (Valenciennes, 1835). The concentrations of NaCl and MG at which growth of both species was inhibited were higher than the respective mean 96h median lethal concentrations (LC50-96h) for silverside eggs. In the case of F, the growth inhibition (GI) of F. solani was achieved also at concentrations higher than the respective LC50-96h. Only for F. semitectum a complete GI was observed at a concentration lower than the LC50-96h. This indicates that the efficacy of these substances is not adequate for treatment of fungal infections of silverside eggs. Copyright © 2012 Inderscience Enterprises Ltd.