If you're using just the smaller of the two HD tubs you'll be fine leaving them alone. You can use an upside down bowl but in my experience it will get moved around. If they are hungry/thirsty they will get the food or water. They can hang upside down on the mesh if need be or stand on their hind legs. You can add a little more bedding if you would like so that gets them a little closer but trust me they will reach it when they want it.