Tubs can only be used if the room has a higher ambient temperature around 76-78 degrees because belly heat in a tub will not keep the air temperature up. Get the 20 gallon off your friend, it should last your snake another year or so. Then use the 10 gallon you have now for your new snake you plan on getting at the expo. By the time he out grows the 10 gallon, you can switch him to the 20 gal and buy the 40 gal for your first snake.