Short of a nuclear bomb, I'm not sure there's anything to get rid of the lovely Florida Fire Ant. We've poured boiling water in the mound, but they usually just pop up somewhere else in the yard. We've also done boiling vinegar. Kills the grass but helped control the population a little better than just water.
Every year about March, we put Ortho Max Bug-B-Gone on our yard. We do it to prevent fleas and ticks, but have discovered it really helps with fire ants, too. You can get it at Lowe's or Home Depot, and lots of other places I'm sure. It doesn't have any ill effects on the dogs and cat.
Anything boiling with kill the grass and as Jen said, they just pop up somewhere else. My pest contol dude puts down some stuff that kills em good. It is in granual form. I water it in an hour after he leaves and it won't bother the dogs. I will have to ask him what it is next time he is here.
The boiling water (with vinegar) did a great job!... At making them mad. (It was kinda fun, though.) I think they go down too deep in our sandy soil. Maybe if you kept doing it untill they give up... It's probably going to take a poison barrier to keep them from coming up, or a bait that they take down to the queen.
I'll look into the Bug-B-Gone, and if you find out anything, Joe...
If you don't mind chems that is the best way. I treat my yard twice a year with Ortho Max and don't have an ant or flea problem. Unfortunately, it does not work for yellow jackets which have returned this year with all the rain.