T_ Tfcjff he effectiveness of EarthTec compound against the monogenetic trematode Dactylogyrus lamellatus was assessed, using 14 different concentrations, ranging from 0.03 to 60.0 mg Cu/L. The result indicated that short bath treatments at concentrations ranging from 42.0 to 60.0 mg Cu/L could kill the parasite, however, they might be toxic to the stressed grass carp. Concerning long bath treatments, it was found that the concentrations of 0.03, 0.06, 0.09, 0.12 and 0.15 mg Cu/L can eradicate the parasite after 120, 96, 48, 48 and 24 hours respectively. These subacute levels of the test compoumd showed no toxic effect on the grass carp.