You really do not need a UV. A UV will at best control or reduce the intensity of a parasite infestation, but it will do nothing to rid the system of the parasite. Fish often die from parasites, look bad with white dots or other markings covering them from the parasites, live shortened lives, and have reduced activity or a variety of abnormal behavior, including eratic swimming, constant scratching or rubing behavior, excessive hiding, or darting behavior. I find it very hard to enjoy fish when they are in this diseased state. Moreover, any benefits UV provides for killing algae can be achieved more effectively through other means, like good skimming, growing macro algae, carbon dosing, and other means.
As far as dealing with parasites and disease and as I mentioned in the club forum you also posted in on this topic, you are MUCH better off investing in and using an appropriate quarantine system than UV. I do no have strong enough words to emphasize the importance of this, particularlly for someone who is new in the hobby. Quarantining is maybe one of the most important things to do for marine systems. You will find that parasites in the marine hobby are a much more serious and common problem than in freshwater and cannot be treated in the display tank like they can be in freshwater. As such, it is a complete nightmare when you have a stocked marine system with parasites. The only way to rid a marine system of parasites is often to remove all fish from the display tank, treat the fish in a separate system (which needs to be large if you have a bunch of fish to treat) with harsh chemicals or difficult to maintain low salinity and not return the fish to the display tank for 8-12 weeks. When you have a bunch of fish, you can see how onerous this process can be and even then it sometimes is unsuccessful requiring that the process be repeated.
In my experience, the two main reasons people quit the marine hobby is parasites and difficulty controling nutrients and resulting nuisance algae. If you focus your efforts on avoiding parasites and disease and having appropriate filtration and stocking, you will avoid most of the major problems which cause new people in the hobby to fail.
