I have never heard of a dragon doing such a thing. Can you try to get him to go to the bathroom in the
bath instead? Some of us on here have trained our dragons to go to the bathroom once a day in a tub of water. To encourage him to do so, just feed him a big meal, wait about an hour then give him a warm
bath and massage his tummy. They have an easier time going in the tub so he may stop going in his tank. The only drawback is you should
bathe him once a day for a few minutes so he can go to the bathroom.
This is honestly the only thing I could think of to do. That's just crazy!