I have to suggest NOT keeping a clam of any kind in a nanocube with only power compact lighting no matter how many PC you have. The reason being that the lumens/watt on PC is soooo low and they are very inefficient in that over half of the light emmitted doesnt even make it into the tank. I too would suggest a mH for that tank in order to keep a clam happy.
Also, there are lower light clams, but they get much larger than the light-loving maximas and croceas.
That being said, there is much more to keeping clams happy than just lighing. You would need to moniter at least your Ca and Alk, and you may also want to know what you pH is at during the day and night, and also not have much of a swing in temps or salinity.
I hope that helps.
Jesse