I have a couple Crocea clams that use to sit on my sand bed, I now have a barebottom tank. I orginally put them one the bottom sitting upright, all fell over after a couple days. I can't get any of them to stay upright for more than a couple days at best, is it flow maybe or do they just not like barebottom? I don't really want to put them up on the rocks, but is that the only choice i have?