I would not advise trying to move the tank with water in it. Assume you will have to rescape things when you arrive. Have you tried to drive somewhere with a half cup of drink with no lid setting in the cup holder ? Remember how nervous it makes you thinking about it all sloshing out? Driving three hours with even a gallon of water sloshing around is going to be far worse. Any water in the tank will make the sand and plants look like a barrier island in New Jersey!
A good quick stop might let it find enough hard stuff to blow the end out of the tank.