As pointed above, Ants do farm Aphids.
We recently had an ant problem (non-gardening related); Here is what to do.
Mix a bowl of boric acid (borax) and sugar water, and put it near the ant trail. The Boric acid destroys the ants from the inside out. Since it is mixed with sugar, the ants will carry it back to the nest and feed it to the colony, ultimately wiping out the entire herd. The trick is to get the right amount of boric acid to sugar-water ratio: Too much boric acid will kill the ants before they get back to the nest: not enough boric acid will not kill them.
Here is a link with some more info. Just google around a bit:
http://homeguides.sfgate.com/homemade-ant-killer-boric-acid-74569.html
I also discovered that Lysol Disinfectant spray immediately annihilates ants right in their tracks. However keep that shit away from your plants as well as your lungs.
Happy Trails