clam question?

[badjuju]

I bought a few live clams from albertson to feed to my mantis shrimp. I figure they would die in the tank. I came in this morning and checked the tank and they are still alive. In fact the buried themselves partly int he sand and I see the tube sticking out. I tapped it and it retraceded it and then came out again a few minutes later. How long will these last in the tank? I thought they only lived in cold water and that warm water would kill them. Any info on this would be nice.