Putting them in a 10 gal would be like putting you in a child's closet with only a bed. You probably won't move around alot, and would be sleeping a lot, but you'd still want some extra room in there!
Really, there is no comparison. A human is a human, a fish is a fish. Of course a much more complex being wouldn't be put in a closet.
With good filteration and water quality it is indeed possible. Conisidering a 25H is only 4" longer than a 10, that isn't a big difference. You only have 2" more width and 12" more height. Again, no big difference.
Bangaii's only grow to 3", and at that it takes them a few years until full growth. They stay and hover in the same spot for hours on end, only to be more active at feeding time.
Think of where the bangaiis came from in the beginning. The ocean. And how much space did they have in the ocean?
As of now, Bangaii's are being captively bred and it's very sucessful. Not all Bangaii's are wild caught, ask Bang Guy! Even if they are WC, they don't occupy over a ft. of territory unless a huge harem. My point is even though that ocean is huge, a Bangaii' would be like an aquarium fish occupying 10 gallons out of 25 million gallons. Not much at all.