And take a look at the way this university suggests rearing grays: (for laboratory research, not pets)
http://www.biosci.missouri.edu/gerha...0husbandry.pdf

by our standards, this approach is positively spartan, and I would go so far as to say the frogs might not be as "happy" as they would be in a large, naturalistic vivarium. But clearly they've had success with it, and the frogs have all their basic food, moisture and sanitation needs met and it's entirely possible that they don't notice or care about the difference.