ideal bulb for clams

[Eduardo cavalcanti]

i'm currently using a 5200k 150w bulb made by osram. daniel knop recomends in his book the same bulb, but with 250w. do you think that this is the ideal lightning for these critters?

 

[firechild]

How high above the tank is the light? How deep in the water is the clam? What species of clam?
Personally, I would go to a higher kelvin rating but I have had success keeping maxima and squamosa clams under 150W DE MH.