I am not sure what triggers reproduction (i.e. lunar cycle, temp or photo period) but a clam will release eggs and another sperm and when the two happen to reach each other, a larvea is created and that floats around until it is strong enough to atach and start forming an adult clam
so if you were to try clam reproduction, you would need quite a few clams to make sure you have both males and females adequet lighting, and also some sort of filtration that wouldnt kill the lavea that get sucked up into it.
Also, you would have to find out what triggers spawning.
Brian