a light question?

[marie]

I always assumed a watt of light was the same with any bulb, fluorescent or metal halide. So when my icecap ballast went on sunday morn i put my hamilton hood(2 175 halides, 2 no fluor.) on my 75g tank thinking it was the same amountof light. My question for you lighting guru's is why does the tank look so much darker and all the corals are starting to turn brown and are reaching for the light? The bulbs on the icecap were 2 actinics and 2 aquasuns. The hamilton hood has 2 6500k metal halides and 2 40w no's.