I don't know too much about any of them except for croceas like to be on a rock. Once I put him in the tank, I watched him for about an hour and realized he kept snapping his shell to get off of the rock I had him on, so I put him on another rock and you can watch his foot start to go down. He has been fully open in the exact same spot since and you can see his foot firmly planted on the rock below. He seems to be very healthy, i was told they should be sensitive to shadows and when i run my hand over the tank, he closes up but comes right back, he seems to be doing very well. In short, after an hour and moving him, he planted right away.