jasno999, Most people will tell you water quality/conditions in a 10G (Nano) are hard to maint. They would be correct. However, a Crocea clam only gets to be about 6 inches, so its a great nano possibility provided you supply a good sand bed and room to grow. You must consider though that water flow, lighting and feeding in such a small tank may cause challanges. Imagine feeding a clam in 10G. 1 feeding you will have significantly polluted the tank. (They filter feed). Again though with strict prompt maint its a very possible scenario with a small clam. If you decide to do it please do keep us posted, maybe some photos.
Peace.