Nose rubbing is a tough problem. I've struggled hard with it. In the end, the only way to stop it is to cover his view out of the tank. Line the bottom of the tank with six inches of cardboard, newspaper, whatever, just to block his view from the floor of the tank.
If he climbs and sees out, he's not in the right physical position to snout-bash and nose rub. That 6 inch blockage won't depress him at all, if he has stuff to climb on, even a broken concrete block stack.