waste of money.. the 13watt UV will burn out in 3 to 6 months. I would return it and looking into other alternative to clean water.
such as Phoshate ban 150 reactors.
Phosban reactors running granular ferric oxide only bind phosphates and won't help clarify the water. You can add carbon in the upper portion, to help clarify the water. However, results are only temporary until the carbons absorbtion capacity is depleted and has the chance to leach back out into the water column. I'm not a fan of running carbon in fresh water tanks as I believe it will strip beneficial trace elements out of the water as well as impurities.
UV is great for killing water born algae and pathogens. Downside is obviously, you have to replace the bulbs every few months.
Slow flow rate through the UV is critical for its effectiveness as it needs enough contact time to kill what passes through.
You can consider investing in, or even DIY'ing an upflow/fluidized sand bed filter inside your sump. Does a great job of polishing the water to a crystal clear state, and will increase your bioload potential. I'll try to post up some pics of the one I built, but only after I get a new camera. Damaged my SLR during summer vacation!