Depends on the depth of the tank, and the size of the clam?
A derase clam is probably your best bet unfortunately a maxima would be out of the question, but in a bio cube i'm not sure id want to chance it as they really do need good water quality in order to survive, also when buying a clam you need one that is approx a minimum of 3" as at that size the zooanthalea algae that they need to survive will be at a stage that lower light levels shouldnt be detrimental to it, but also remember you need to add photyo plankton into the water as food for the calm to give it the best chance, all this is still dependant on the depth of the tank as well
I Have to say that you need to be very cautious of adding one in such a small environment. but its not impossible to keep one, just think very carefully and ask more questions before you add one as most people seem to add them only for them to alst a month or so, also if you do decide to get one make sure its been aqau cultured (all should be as im ure its now illegal to take them from the ocean) which will mean its already adapted to being in an aquarium