personally i dont like them there r people who swear by them and then people like me who dont believe in using them..i guess its a personal opinion of what u want...people say it helps keep there water clearer or they see less algae blooms in there tank or it kills ich right away ....so i guess its one of those things u either believe in them or dont...i hope i was at least able to help u alitter you can pm me if u need more info
ich also leaves strands in your sand bed so i dont believe it completly kils any parasitic organisms i think it jus reduces whats circulating thru the uv,also for it to be effective u have to have clear water in the beginning and a slow flow thru the uv
a uv works two ways, depending on the watt's and flow, it can either be used as a clarifier\algea destroyer or to help with parasites, this all pending the flow you use it at. only one brand i reccommend is the aqua uv they give real data unlike almost all the other companies. i have been using one almost a year now and wont go without it, guess it is one of those thing that you dont really see the benifit of but it is there
I used one for a few years. It did make the water more crystal clear. It did cut down on the algae and may be the cyano growth. As far as ich, I don't know if it made a difference (my tangs used to get ich around this time of the year when there is a larger temp swing). Setting the correct flow rate through the UV can be tricky. Maintainence of the unit (keeping the quartz sleeve from calcium deposite and hence blocking the UV light) can be a real PITA. I stopped using it since 2008 and my fish (tangs) are healthier than ever.