I feel for your problem. I have no personal experience getting rid of fire ants. I have dealt with them and a few other ant species though when I lived in western Miami (basically Everglades) and they were always trying to invade our home that was surrounded by vegetation.
I found this website but can't vouch for how useful it will be.
When I dealt with non-fire ants I used a diluted borax/sugar/water mixture or just borax/sugar mixture. Borax can be toxic in concentrated doses so do your research on how and if you want to use it. Things to think about are how it affects your skin, can affect aquatic organisms, and how it acts as an herbicide. Know your dilutions.
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