Just wanted to add that I had my Chinese in a nano tall (8"x8"x12") and while it does fit the size requirements, it can be a bit cramped, especially for an active species. I bumped him up to the 12"x12"x18" and he seemed to enjoy the extra space, always roaming around. After he died, I got a wild-caught adult female Chinese and she is in that one now and she's also benefiting from the extra space. And as mentioned, it does allow you to decorate more without taking up their space too much.
Some species can also do well in large mesh enclosures which are cheaper, so if you want to give them more space without spending as much money, that could be an option too.