In summary, some people swear by them and some people swear at them. UV is undisputed in being effective at clearing green water. If a high enough UV dose is applied (namely using a high-wattage UV bulb and low flow rates), UV can kill pathogens; Keep in mind that ich is very UV-resistant. While UV likely won't erradicate a pathogen that is in your system, it may be able to keep the pathogen population at a level that the tank inhabitants can cope with. If you decide to go with UV, aqua UV and Lifeguard seem to be the two most-regarded. Look at their data sheets to find the combination bulb power and flow rate you would need to accomplish your goals.
