Ice cubes to clean black tank

Our Phoenix Cruiser has the SaniCom system dump and built in washers, a new experience for me. It seems to work pretty well. I have always found that after dumping, a two thirds tank full of fresh water, a little Tide or equivalent and a hundred miles down the highway before final dumping is the easiest method for me.

I tried the ice a couple of times, using a full bag from the convenience store. Only thing I got was CC....aka Cool C***.