Thankfully we don't have fire ants around here! Diatomaceous earth works with regular ants and I've heard of folks using it to dust dogs for fleas. Perhaps you could gather some information on this. They do make a food grade Diatomaceous earth.
I dump a very large pot of boiling water right into the ant hill. It kills the queen.
I was told to pour club soda right into the mound- has always worked for me.
