I picked up this clam a few days ago. My picture taking abilities are lacking but you get the idea. The light blue areas are really bright blue, the other colors are true to form. I learned a lesson a bit too late. You should place your clam on an old clam half shell or a small movable piece of rock. Rock dwelling clams like croceas attach themselves to the rock work. Which is cool until one morning when you wake up and your clam is facing toward the back of the tank...not cool. I was able to slowly twist mine back the way he was and he seems content again for now. I knew which way he had twisted so I felt pretty safe slowly untwisting him. The clam attaches with byssal threads and you have to be really careful about not damaging the byssal gland. From reading about this on clamsdirect.com forum it is risky to try to move clams. There are a couple of methods of totally liberating a clam from a rock but you are taking a chance when doing so. If you place them on a movable base you can reorient them if they get into an undesireable location. You also have to consider why they might be moving if they do it constantly, they might not be happy where you have placed them. Since they are on a movable base you can easily try a different spot if need be. Live and learn. I got off easy I think and I hope this experience helps future clam keepers.
