Just over a year ago, I wrote about using a cat food moat to foil an ant invasion. That worked well for a short while, but it got old real quick. For one thing, my cats and dog were always pushing the bowl close enough to the edge of the tupperware that the ants could still get in. For another, the cats are such messy eaters that the cat food was always getting into the water, creating the most disgusting slimey mess. Very gross.
One year later and my ants are gone for good. It was a 2-part solution, one part of which was pretty obvious. Plug the holes into the house.
I caulked the path into the house that ants were using. They almost immediately found another one. I caulked that too. And repeat. Many many times, repeat. It helps to let the little ants stay alive and well in the house because they will help you find more holes as they try to find their way back out of the house.
The second part of the solution is cinnamon. Ants will absolutely not cross it. If you have an area that you cannot seal, such as a doorway, create a thin but continuous barracade of cinnamon. Seal it if you can though, because too much cinnamon everywhere just ends up being a big mess as well.
Totally non-toxic, safe for pets, natural.