If you are worrying about him running out of oxygen, don't. Unless your enclosure is sealed like a refrigerator there is no way he could use it up faster than it leaks in.
He would probably be fine even if it was perfectly sealed, because every time you open it to feed him, or soak him, you would be letting in lots of fresh air.
He would probably be fine even if it was perfectly sealed, because every time you open it to feed him, or soak him, you would be letting in lots of fresh air.