UV is beneficial, only if implemented correctly with the correct flow dynamics and without any DT water recirculation within the UV setup. UV does not kill any bacteria that is living on your rock or surfaces of your tank and most and not all are killed by a UV system. You will need the correct globes and the contact time is very important along with the spacing between the globe and the UV wall. One should also have a quartz sleeve surrounding the globe.
Sadly most UV systems are not really beneficial.
I personally use a TMC type of UV system that has 4x55W globes that run through a closed loop with a pump that circulates the water at 5000l/hour. I have never HAD any WS or parasite that has a free living stage, and I have introduced fish like a powder blue and various angels, without quarantine.
Connect it up, it wont hurt.