Why is the greasy film that used to end up the dog bowl no longer there since adding Shungite?
You are talking about "biofilm". Biofilms are microorganisms that can be bacteria, fungi or protists growing on the side of the bowls. One other example biofilm is dental plaque. It is not hard to imagine dental plaque bacteria in the pet's mouth feeds the biofilm in the bowl. This is one of the examples that Shungite is working. Microorganisms that should not be in the water are simply destroyed in a Shungite environment.