David D,
The reason grits did not work on your fire ants is your ants are the southern type. When you throw grits on a northern ant hill, they fear white trash or Jeff Foxworthy has moved into the neighborhood and the ants quickly move. The southern ants just aint that proud. You might try playing some opra or rapp over their ant hills.
Seriously, I would think that if it is a very large colony, it will take a lot of grits to kill them off. Just don't get caught wasting good grits down there.
