Definitely not regular ant killer with borax in
"The estimated lethal dose (ingested) for adults is 15-20 grams; less than 5 grams can kill a child or pet. For this reason, borax should not be used around food. More commonly, borax is associated with skin, eye, or respiratory irritation. It is also important to point out that exposure to borax may impair fertility or cause damage to an unborn child." from a proper chemistry site.
I had a look and there are all kinds of tips. One says use a 50/50 mix of water & white vinegar in a spray bottle. One says to use instant grits (ground corn) it says that they eat it and it swells in them and kills them.