UV sterilizer help

I am considering purchasing a UV sterilizer for my 55G reef. A few places i have looked at have them, but they vary in size...i want to know how many watt UV sterilizer i would be looking for in order for it to be effective but not overkill. Will a 9 watt do it?

 

I have a 9W Turbo Twist. I Put a separate pump that I have on there with a ball valve to restrict flow. I started my reef tank with it so I don't know how effective it is but I run about 50gph through there (to kill EVERYTHING parasites and all).

 

You always want to oversize the wattage to account for bulb degradation that happens.

 

yeah i know but the size of the unit it's self is huge for the 24watt, i don't want to use a ton of space if its not needed

 

Agree with DanK, if your going to use a lower watt bulb I would just decrease the water flow to add exposure time or maybe get one of the twisty UV tubes. but idk, i dont even use the one I have in system. But some makers test their bulbs at full strength and some at the bulbs half-life. I like the latter bc you know where the bulb will be in terms of killing power in ~6 months.
best

 

I run a 15watt aqua ultraviolet UV sterilizer on my 50 gallon.