The tank is lit by a PFO dual EYE ballast with 2-250W Iwasaki 6500K bulbs surrounded by 2-48"
NOVA T5 retrofit units and 2-36" NOVA T5 retrofit units with 460nm Actinic bulbs.
The actinic lights are on an Intermatic dial timer and the metal halides are on an Intermatic Heavy Duty Digital Timer. The actinic lights come on for a period before the halides and remain on after the halides go off for a dusk to dawn effect. This is with only the actinics.
This is a picture with both the actinics and the metal halides.
Without actinics, the 6500K lighting is yellowish in color. But, 6500K is the spectrum of natural daylight and encourages good growth.