Very true.
Also, I have a Big snail in my tank which I believe is some kind of whelk. It's been in the tank for a year now, and it makes a beeline for the Clam as soon as it's injured. It eats the injured clam but ignores the non-injured littleneck clams.
I find it convienient to keep this food live and in my tank, ready for feeding, though I feel guilty killing anything in my tank, even though it's a food item anyway...
At the end of the day, I can just pick up the clamshell, and any un-eaten remaining inside. Very tidy. My skimmer doesnt go crazy, so I'm assuming that the clam doesnt start to decompose right away.