In the present study, fungicide activity of Thymus volguris essense on the separated fungals from Koi fish's skin was studied. (aspergilus felus, aspergilus fumgatus, aspergilus naijer, and saprolgina parazitica) on skin were separated and determined by using  slide culture method. The least Inhibitory (MIC) concentration of fungal growth of (aspergilus naijer, aspergilus fumgatus, and aspergilus flaws) species by using Thymus vulgaris essense were 25 microleters concentration, But it was different and was 50 microleters in (saprolginia parazitica) species. The least  virulence (MFC) concentration of fungal also in (aspergilus naijer) and (aspergilus fomgatus) species were achieved at 100 microleters concentration and inn (aspergilus flaws) species were observed at 25 microleters concentration. And, MFC in (saprolginia parazitica) was observed at 25 microleters concentration. The most Inhibitory effect of Thymus volguris essense was on (Aspergilus flaws) and the least Inhibitory effect of this essense was on (saprolgina lgina parazitica). According to the obtained results, Thymus volguris essense may be used as a substitution of commercial fungicide medicines in aquaculture industry.