I have two cats, and each requires its own special diet for nutritional and health reasons. How can I prevent them from eating each other's food?

Offer them several small meals a day but feed both of your cats on a fixed schedule. Create enough distance between their food dishes so that they get used to eating at separate meal areas and pick up their dishes after each meal.

Initially, you’ll have to supervise at meal times to make sure they don’t steal food from each another. Soon, the novelty of trying to sneak “forbidden” food will fade.