I typically skip the mid size tub and go straight from a 6 qt for hatchlings (roughly 14" X 8") to a 28 or 32 qt tub (roughly 24" X 16") for sub adult/adult sizes. smaller males can stay in a 32 qt for the rest of their lives but larger snakes and females get moved up to a 41 qt tub (roughly 35" X 16")