Go to your local ag store and get you one of those recycled rubber feed/water tubs/bowls. They have them as small as two quart or smaller. Then you can just bump it and the ice will pop out. You can’t tear them up. I know, because I have ran over them with a tractor more than once. Another thing, if you use a regular hard crock, you don’t need to fill the crock all the way to the top with water. The rabbit won’t drink that much between waterings and you will have room for the next time.