Use Vinegar! We had this problem in one of our apartments. The ants literally went from our balcony sliding door right to the dog food. I put vinegar in a spray bottle, sprayed the track of the sliding glass door, the balcony, and the carpet to the dog dish and under it. No more ants. I've done this in my current home on counter tops, door frames, carpets, everywhere. No worries.
I don't know if this would work in the garden since vinegar is also a short term weed killer, but it may work on the ant mounds.
By lkaserman from Adelphi, MD