Antifungal and toxicity effects of new combined essential oils on Oncorhynchus mykiss in comparison with malachite green

mold infection is one of the most important problems in aquaculture. recently, administration of some chemicals such as malachite green in order to control mold infections has been limited in aquaculture. in the current decade, researchers have been more focused on using herbal extracts and essential oils in aquaculture. in this study, minimum inhibitory concentration (mic) and minimum fungicidal concentration (mfc) of a new combination of four essential oils (eucalyptus globulus, mentha piperita, salvia officinalis and thymus vulgaris) were determined by serial dilution method. lc50 of the combined essential oils for 48 and 96 hours were then determined on oncorhynchus mykiss fingerlings. mic and mfc of combined essential oils were 0.025μl/ml and 0.050μl/ml for f. solani and 0.018μl/ml and 0.035μl/ml for s. parasitica, which was lower compared to malachite green. it was also 0.060μl/ml and 0.300μl/ml for f. solani and 0.045μl/ml and 0.120μl/ml for s. parasitica respectively (p <0.05). the results of lc50 for 48 and 96 hours were calculated equal to 34.98ppm. based on these results, the combination usage of essential oils can be proposed as a good antifungal therapeutic strategy in hatcheries.