How can you tell if a crocea is healthy?

[anomie]

About three weeks ago I purchased my first crocea clam. Like most people, ( I assume) the color and pattern were the main factors in deciding to purchase. <---Not counting the requirements needed for various clams.

Anyhoo, I did the little rock trick under the sand until it attached and now it sits about 10 inches below the water line directly under a 250 watt halide. I have since noticed a slight tear in the mantle that has been healing. All of this lead me to wonder what , if any, are signs of a healthy, happy clam in a home aquarium? What about in the store? What should I be looking for besides growth?

A couple of blurry pics too.....

Sorry about the reflection