Originally Posted by reefbound
I do realize that, also the depth of the tank matters too so the lower you go the less wattage you have...
the wattage of the bulb will be the same if you are 3 inches from the bulb or 3 miles from the bulb. lumens and lux are used to describe the "brightness" and "intensity" of the bulb.
the watts per gallon rating is only a starting point for selecting a bulb. you really need to have a lighting system with enough "penetrating power" to get the proper amount of light (lux) for the depth of your tank. notice i said lighting system... not bulb. there are several things like distance from the bulb, type of bulb used, reflector design... etc.