WOW! I am doing a build for a 55g tank and I am using 36 3w LED's with dimming because I figure I might have almost too much light.
I heard a formula for calculating how many you need (doesn't work for really deep tanks):
Length*Width/18 = # LED's
Here is a site for finding your dimensions:
Chart of Tank Sizes
What is the ratio using blue and white leds? Or is it just straight while leds?