Just found this chart for Max flow rates for each wattage. Seems accurate. If so, then 8W-9W is probably not effective against parasites which correlates to what I'm seeing in my tank. I'm sure it helps a bit. Its just not that significant for me.
http://www.liveaquaria.com/general/g...ral_pagesid=21
Code:
UV Rating Bacteria/Algae Kill Dose Parasites Kill Dose
Watts Max Flow Rate Max Flow Rate
8 120 GPH N/A
15 230 GPH 75 GPH
18 300 GPH 100 GPH
25 475 GPH 150 GPH
30 525 GPH 175 GPH
40 940 GPH 300 GPH
65 1700 GPH 570 GPH
80 1885 GPH 625 GPH
120 3200 GPH 900 GPH
130 3400 GPH 1140 GPH
EDIT: Found another
http://www.drsfostersmith.com/pic/ar...id=423&aid=440
Code:
UV Bulb (Watts) Bacteria and Algae (gph) Parasites(gph)
4 60 N/A
8 120 N/A
15 230 75