Wow, SB, I never considered painting the outside of a tank with the KBS. It might make one heck of a paintable surface. I spilled some on my garage floor and it's still there, hard as a rock and nothing seems to have any effect on it. I also poured a little of the leftover into a crack in my driveway where ants kept coming up. Almost two years now and no ants.
Keep the progress coming. We're all watching.