Passin Thru
Sir I saw a show on TV and I believe it was on an RV website that disproves your thoughts about ice in the black water tank. The guy on the show made a tank from plexiglass and mounted it in his pickup bed. He used bread dough and muddy water for his test along with some TP. He filled the tank then emptied the tank leaving the sides dirty and some clumps. He then used 10 gallons of water and 10 gallons of ice, went for a drive around the block ("several times") and then emptied the tank again. No change in side color and a little bit of the clumps came out, but did leave some. A basic rinse would have done the same job.
But to each his own, I rinse.