Question about clam

[Borderjumper]

Originally Posted by Oilers

I have recently purchased a couple crocea clams and lost both of them today. I was placing them on the rock and noticed that they were knocked down to the sand a couple times. I picked them up and put them back on the rock. This morning, they were not at where I put them last night and I found them on the sand again but only the shells were left.
What would likely to knock the clams off the rock and what would have eaten them? If I get more clams in the future, what should I do to ensure their survival? Do I need to glue them on the rock? Thanks all for your help.

I wonder if they were healthy when you got them? they should have attached to the rock and been unable to get knocked off. When you purchased them were their "foot" intact?