The aim of this study is to evaluate the anti fungal activity of a combination of essential oils against water molds. HPLC analysis was done to evaluate the quantity and quality of the active compounds in this combination which extracted from three herbs( Peppermint Menthapiperita ,Thyme Thymusvulgaris, Common sage Salvia officinalis L.) and the active compounds are Camphor,Menthol,,Thujone and Thymol with different concentrations. In this study (MIC) , (MFC) were measured and (LD50) determined after 48,96 h from fingerlings treatment of common carp in aquariums .The results of (MIC) were 0.025µl/ml for Aphanomyces sp. and 0.015µl/ml for both Achlya sp. and Fusariumsolani which showed significant differences(p<0.05) from Malachite green concentrations which were0.06µl/ml for Aphanomyces sp. and 0.04 µl/ml for both Achlya sp. Fusarium solani. According to the results of (MFC) were 0.06µl/ml for Aphanomyces sp. and 0.02µl/ml for both Achlya sp. and Fusarium solani which showed significant differences(p<0.05) from malachite green concentrations whichwere0.4 µl/ml for Aphanomyces sp. and 0.25µl/ml for Achlya sp. and0.3l/ml for Fusarium solani. the results of (LD50) after 48,96 h was34.51 ppm and there were no differences in LD50 concentrations after 48,72,96 h after adding the combination to the aquariums
