The tub will be fine for now. I also recommend a 4x2x1 1/2-2 when it is adult. Once it gets too big for the tub I would just move it to the 4x2. Carpets aren't like balls and they do move around more and don't mind a bigger space. They are a pretty hardy snake. In my 4x2 I also have a couple dowels spanning it for him to perch. Jungles will do a bit of climbing when older as opposed to coastals which stop climbing as much when they are older.