well the hognose only gets 2 ft and they feel stressed and insecure in open spaces, they are recomended around a 10-20 gallon, mine is 21 so should be perfect, i have done lots of research on these, as i was going to get one last yr, i recently watched these vids of expert village about care of them by this american reptile guy.
How to Care for Hognose Snakes | ExpertVillage Videos
in the wild they would keep to small burrows and hides to feel secure and dont venture out into open spaces too often, this is why a viv can be too small but also too big. i think mine is just right.