Losing the war against Red hair Algae

I am losing the war against red hair algae in my tank. My nitrates are 0
and and my PH is steady between 8.0 and 8.2. The temperature of the tank is
between 80 and 82 degrees. I have (2) 250W metal halides that are on 8
hours a day and (2) 45 Watt actinic lights that are on 12 hours a day. ( I
don't have a phosphate test kit...could that be the problem?)

The red hair algae does not grown on the live rock much. Instead it grows
every day on the sand. I rake it each night until there sand is white
again, but the next day it grows right back. I have crown snails, astral
snails, some unidentied snail, emerald crabs, blue legged hermit crabs,
brown lagged hermit crabs, but nothing seems to eat it. Any ideas?