Yes that's a good idea with the whole tupper ware/
bath tub thing. Most dragons usually LOVE the water. But it's hard to tell until you
bathe your dragons for the first time. 7 inches is plenty big enough to
bathe him. Just make sure that he isn't overwhelmed! Some dragons will play in their water while some dragons will sit there looking kinda shocked. If he starts trying to run away just take him out. I'd say 1/2 inch of water would be best. Sometimes they'll drink so don't be alarmed if he dips his nose in to the water. Just make sure his whole head doesn't submerge. Some people put a small moist hand towel in their
bathing tubs so the dragon can crawl out when he's done or just hold on to the side of it to make him feel more secure. Paper towels work as well just make sure they can't get trapped under them while playing.
Oh be sure to take pictures of his first
bath for us! Haha