[tang daddy]

I have 5 croceas and all are on rocks, I'll agree they are hard to get on the rock here are some suggestions to help you....

Find a rock that is slighty convex sort like an upside down saucer place the clam in put a few rocks around it so it cannot fall out sort like baby in a craddle they will attach overnight. Another thing to keep in mind if once attached to the rock make sure they are always facing up cause sometimes if they are side facing the weight of the clam is too heavy for the legs and they end up releasing happened to me before aswell.

The only one that doesnt take to rock in my tank is a gold clam, derasa?

It just sits on BB tank and moves around on its back the legs don't anchor either, kinda weird.