I found Bengal fire ant killer works really good on fire ants.
I disturb the nest then sprinkle it on the ants crawling around.
They take it back into the nest and most of the time the nest is dead the next day.
Is it fairly new? When we lived in SC, folks were trying anything to kill them...grits seemed to work consistently...blew ‘em up.
Don’t have a problem here in the desert with fire ants, but the carpenter or argentine are a nuisance...get into food if it’s not secure.