I currently have an 18 watt turbo-twist on my saltwater aquarium. I have it plumbed in line on the return of my eheim canister filter...it works great right there. If your planning on hooking up multiple components to your canister filter you should check your particular canister filters parameters just to be sure. You don't want to wear out the pump too much.
A few things though...
It definately needs some sort of filtration "in front" of it. The clearer the water is when it passes in front of the UV
light the better it will work.
sterilizers are meant to be used continuously. If you only run it a couple hours each day, the parasites, bacteria and algae will pass untreated the rest of the day.
You also need to watch the water flow...parasites require a slower flow rate to be affected by the UV
light than bacteria or algae.
Regular cleaning of the quartz sleeve as well as making sure to replace bulbs after time are also important in the sterilizer being effective.
Hope this helps!!