This is all getting a little confusing, so I feel the need to point out that both gallons and cubic feet are measures of volume, so unless there is a difference between American gallons, English gallons, Canadian gallons, and Australian gallons, as well as cubic feet, the same number of cubic feet is going to be equal to the same number of gallons no matter where you live, although there may be differences in opinions about the minimum size of a tank for an adult bearded dragon, and differences in the way the tanks are labeled and sold in different countries.
Example: 1 cubic foot = approximately 7.5 gallons (according to my research). Our beardie's tank is 6 feet long x 18 inches (1.5 feet) wide x just under 2 feet tall, and is considered to be 125 gallons, and if you do the math, it comes out approximately right. Our beardie is a little on the small side of average for an adult at 17-18 inches long, so he doesn't seem to have any trouble turning around in it. We considered a 6 x 2 foot tank, the next ready made size up available, but it was too tall for me to reach him on the bottom, and we would have had to get one custom made to get the extra floor space without the unwanted extra height (taller than my arms are long), so we decided this would be adequate for the price... :roll:
And BTW, they all have their own different individual responses to the "ghost beardie in the glass". Luckily for us, ours seems to know that his "little friend" is there, but doesn't seem to want to fight with him or get too crazy about it. We're really not sure what he makes of it. :?