Do Ice Cubes in the RV Black Tank Really Work?

I did it once with great results. Dumped the tank, checked the control panel and all lights were lit like the tank was full. Put about 10 gallons of water in the tank. On my way out of the campground I stopped by the store and bought three bags of ice, broke them up real good and dumped them in the tank. Two minutes later I was on the curvy canyon road for the next 20 miles. Dumped when I got home and the tank monitor showed empty. Stayed that way for a year or so. The trailer was a Montana 3485 5er.