Honestly I feel that there should always be a hide, a tub would almost never mimic one. Especially if the tubs are the white translucent ones most use. Even if its dark, whatever light you have goes into the tub so those tub walls wouldn't look very secure to them. Also they don't get that tight enclosed space feeling they would unless the tub is too small for them. When you put a hide into a tub, most snakes would start using the hide, they prefer it. So i'd give them the choice.