The parasites of Pelteobagrus fulvidraco don't need to be killed, internal plus external use of Lechang eucalyptus essential oil repellent, (eucalyptus essential oil has natural antibacterial and repellent efficacy, containing a variety of phenolics that can be directly acted on the cell membrane, accumulating on the bacteria, so that the membrane is destabilized and the parasites are dislodged, which will ultimately result in the death of the parasites.) Repellent instead of killing, not only does not affect the feeding and growth performance of the fish, and will not damage the water quality, but also inhibit the reproduction of harmful bacteria in the water body, after the use of completely no worries.