In a preliminary study, the antifungal properties of essential oil of Satureja hortensis at different tenderness were tested on potato – dextrose agar (PDA). The fungus Aspergillus flavus PTCC 5006 was isolated from pistachio nut obtained from Rafsanjan area, Iran. Among the essential oil compounds, 500 ppm concentration was completely inhibited Aspergillus flavus growth. After determination of the most effective concentration, it was added to fish feeds compound which inhibited fungal growth and production of aflatoxin. Its concentration was determined as 500 ppm and over of essential oil of Satureja hortensis. The essential oil of Satureja hortensis was analyzed by means of GC-MS and their effective factors were evaluated for fish feeds and their results are shown in tables
