Most people keep them in clear rubbermaid type containers, ranging from 6quarts/12q/28q/32q/42q. Depending on size.
A smaller aqarium would probably provide more security though. Hides should be just big enough for them to get in, they dont like oversized hides, they like to feel wedged in there.

The reason aquariums aren't the best, is most have open top type lids, which dont allow for any humidity to really hold in the environment. Easily solved with a lid adjustment. Also, glass is such a hastle to move around when cleaning. Its not as bad when you have 1 snake, but as you can see lots of us have 5-10 even 20-100 +. Glass isn't really the best option.

Depends on your situation.