It looks like it is bowed in to me. (maybe???). That is fairly level. I would say it could be the stand,floor, or change in flooring that makes it a little un-level. My 38Gallon is less level than that with no issues, other than I know. But in my case it is the carpeting underneath and the furniture it is on that is causing it. I really don't think it is a problem, but others would know better than I would.