Welcome to the board eric, with my experience the Uv sterilizer kills floating algea, the slower the flow rate the more bacteria will die. I would recomend a UV light anyway, your water quality will improve,resulting in clearer water. for the hair algea what color is it? have you checked your phosphate levels? also Emerald crabs will eat hair algea, but you need to find the reason for it, like high phosphates,hair algea will thrive with high amounts , hope this helps...cya