Room mates for clam

A few weeks back at a frag swap I picked up a beauty of a clam. It was a 21/2 inch blue teardrop crocea. Got it acclimated and into my tank. It was doing fantastic for 3 days. Fourth day, I woke up to see it being eaten by a whelk, which I thought was a nasarrius snail when I got it. Needless to say, my clam is no more and the whelk is looking for a new home. I desperately want a clam in that tank so I want to be fairly sure I have nothing else that will munch on a clam. My inhabitants include a large mystery snail, several chitons, nerite, cerith, and astrea snails. There are also 4 or 5 blue legged hermits. I also have a coral banded shrimp. Are any of these clam predators?
Thanks!

 

what you have left shouldn't bother a clam

 

Fantastic! Thanks.

 

Be careful of all Angelfish and Butterflyfish as they have been known to eat clams.

 

My only othere concern is a coral banded shrimp. No angels.

 

And what is that other "Large mystery snail"??? A pic to identify it would be wise.

 

It's a Mystery Snail... not a snail, the type of which, is a mystery to me.