Contributed by Tokemon
I read a tip a while ago about using Pottasium Permanganate (Condy's Crystals)to control ants. Decided to give it a go. You can get PP at Chemists or some Supermarkets. You only use minute amount and mix it with plain water (just a few grains - enough to turn the water a pale to mid pink, not so much that the water goes purple to opaque). Then just water into the soil.
For me this has worked like a charm. AND IT WORKS ON WHITE ANTS, TOO. Keeps all sorts of ants out of the soil and away from the roots. Didn't harm plants at all.