I just hooked up a 32W to a 180.
Here is the chart I used: http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4393+7999&pcatid=7999">http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4393+7999&pcatid=7999</a>
Also, in the instructions that came with mine, it told you watt GPH to run the UV depending on what you want it to do.
I run mine with a seperate MJ1200 so the light has more contact time with the water. A return pump depending on your application may just jet the water through too fast.
Also, I just got mine from Pet mountain and Linda Lee is doing another order with them if you don't already have the UV.