Well, I won't debate the merits of a UV - I think that is something everyone needs to decide with their own tanks, care routine, circumstances, etc.
My basic opinion is:
Are they necessary - not in all cases
Can they help - yes, in some cases
Can they do harm - only to your wallet
Should you buy one - well you need to decide based on your needs and circumstances.
That said, I posted the following a few weeks ago on the DIY board about my Vecton UV Sterilizer:
Here is some good info here on kill rates and UV sizing:
http://www.tmc-ltd.co.uk/catalog/uv...sterilisers.asp
I ultimately chose the Vecton unit
http://www.tmc-ltd.co.uk/catalog/uv_filt/Vecton_UV.asp
I did this after all my reading (and was swayed by the guidance of some of the salt water guru's over at wetwebmedia.com). The folks who make the Vecton unit really got started in the commercial market (rather than many other companies which just focus on the consumer market).
the vecton unit is not widely sold in the US. You will see it is made in the UK - so not many hobbyists here know of it. You will not find it at Big Al's or most other online stores. I did however find it here:
http://www.fishsupply.com/cgi-bin/f...VZZ/SUVTM-UV025
now I went with the 25 Watt unit which is for tanks up to 150 gallons. the 15 watt unit is for tanks up to 115 gallons. However, if you look at the maximum flow rates for killing efficiency, the 25W unit is about 450gph versus about 340 gph for the 15W unit. Looking at my pump, I am moving about 375 to 400 gph - so I went with the higher rated unit. plus on sale, it was just $10 more
now, I am sure you could find some of the basic retail brands for $20 to $30 less - but I figured if I am springing for $100 or more- I might as well get the best quality and spend $130