Don't know what kind of pump you're using, but if it's a water circulation pump (such as the Hydor Koralia) situated to direct water flow across the front glass of the tank, for example, then place your UV at the rear corner of the tank, fully opposite to, and in the direction of the flow, to enable the UV to pick up and destroy all the free-floating algae dislodged by the pump.
Helps to control algae, especially the film/dust algae.