Since they don't naturally occur with tridacnids, it's hard to say if they would jump on them and eat them...You could attempt to target feed them, but it could turn into a really expensive proposition from Arkansas. You might get them to eat the live clams that are sometimes available at the supermarket. Sounds like a risky enterprise though, especially if you intend to keep them with your giant clam(s). It would be a lot easier if you lived on the east coast.
Cheers,
Don