Why are you adding corals when you have a problem with controlling your nutrients in your tank?
UV Sterilizers only prevent free flowing algae, bacteria, ich, and other living organisms in the water, by making them sterile - or unable to reproduce. Algae such as hair algae, algae growing on the glass, rocks, macroalgaes and the like will not be eliminated with the use of a UV sterilizer.
To get rid of algae, you have to find the source of your nitrates and phosphates such as overfeeding, a poor quality source of top off water, dead/decaying organisms, built up nutrients in crushed coral or sand beds. (that's not the only ways.) and then eliminate the source, or reduce it and increase filtration.