There are four forms of filtration available to us: Mechanical, biological, chemical & disinfection. UV irradiation and ozonation are both forms of disinfection, but can be used tother just as one would use a protein skimmer and filter sock/bag for mechanical filtration.
Ozone is often used sporadically on a timer and or ORP controller. UV on the other hand can run 24/7. Ozone can alter salts and convert bromide into bromine. This acts as a strong oxidant that can harm the display tank residents. UV sterilizers have no residual affect on the the display tank. You only kill the organisms that travel through the UV sterilizer.
UV is considered to be the "safe" method of disinfection, while Ozone is considered to be the "effective" method. In my opinion, the two compliment each other.
Plankton does not pass through a UV sterilizer to ay great extent, and if it should go down that road, it will make it through unscathed. Copepods, amphipods, mysids and isopods for that matter, stay in the substrate and even when they venture out at night for a swim, they are able to stay clear of pump intakes. There is a common myth that your refugium will feed your tank, but it can oly do so if you shake the algae culture out in the display tank manually.
Medicating the food with metronidazole and or chloroquine is the only effective method of treating ich in a reef tank without harming the inverts. There may be some measured success in feeding the fish garlic, ginger & onion, but it sounds more like the start of a delicious tom yum recipe