When I was in this business, ich isn't an issue compared to other "nasties" like velvet, Uronema m., flatorwms, etc. Unfortunately, there isn't much one can do for an ich outbreak in a reef system other than PolypLab Medic and 1/4-1/2 cup hydrogen peroxide per 50gal 3x/day.
UVS will work provided that you have a "zap rate" of 190,000microS/cm2 at a flow rate that it 10x to your DT. Ideally, UVS should be plumbed in a closed loop vs a flowthrough from the return pump. That said, one will drop a "$h!it brick" when one sees the $ of the proper wattage to achieve such a number. All most UVS will do is create water clarity and minimize algal and bacterial film growth rates on surfaces.
Save your $ from buying a UVS and amass a med warchest of malachite green, foramalin and chloroquine phosphate from whatever source you can get them from. A bath in 10xdose for an hour per volume in eht container that the fish are acclimating in. Then a NSW and then a DT water dip to rince off the meds is the easiest you can do compared to the expense, space and maintenance of QT system. In the last 5 years before retiring from this biz, I have been very successful with this method of adding new fish to a clients' system.