UV probably won't touch flukes. They are larger organisms than protozoans like marine ich or dinoflagellates like marine velvet.
If no improvement after 24 hrs with praziquantel (which would not be rendered ineffective by the skimmer if the skimmer top collection cup was removed), then consider using formalin. There are strains of flukes now that have developed resistance to praziquantel from people chronically underdosing it, or using it in systems where it didn't need to be, and bacterial populations build up that break it down before it can do it's job.
Formalin treatment needs to be done in a separate tank, and the display would need to sit fallow around 50 days to have a complete double prepatent period fallow time, guaranteeing none survive to reinfect the fish. A formalin bath, using dilyted 37% formalin before being moved into a sterile quarantine should eradicate flukes, and can be repeated 7 days later, sterilizing and resetting up the quarantine while the fish are in the formalin bath. I use bleach and hot water to scrub and sterilize quarantine systems, and Microbacter7 to prevent ammonia spikes or secondary cycling.
