UV sterilizers are great for treating green water ( micro-algae) in ponds and tanks or if you have a tilapia farm or super high density display tank with bacterial nutrient blooms. In your reef aquarium or quarantine tank they may do more harm than good. Ultraviolet sterilizers kill small organisms. Do you want to kill bacteria and algae, worm eggs and sponge cells; basically floating vitamin packets delivered live to the mouths of filter and muco-ciliary feeding animals such as corals, sponges, and tube worms? People pay a lot of money to pour live phytoplankton into their tanks. Ideally, you don't even need to suppliment live "phyto", your reef is stable enough to provide the plankton to itself. Just watch a few water parameters and do water changes as needed. The sun and our aquarium lights output a certain amount of UV and the balance in nature has evolved to this. Invest in a good aquarium light and let nature do it's thing. In your big reef tank, if you are doing things mostly right, there is no reason to sterilize the water. If you think you are going to cure cryptocaryon from your main system, there is a very tiny chance that this works and it is absolutely in combination with many other factors including water quality, nutrition (possibly medicated food and suppliments), stress levels of fish from aggression, etc. Saying a UV cures cryptocaryon in a reef is like saying bug zappers are leading to the extinction of house flies.