So any deal with fire ants? They are everywhere here in TX and just a way of life. I usually sprinkle ant killer whenever I see their mounds start, but I’m concerned they will move into the hive in the back corner of the yard. Anything different for fire ants or just use similar solutions I’ve seen here
Ant moats - use the search tool and you will find a lot of posts. It was the only thing that saved our hives from Argentine ants which are a real pest here.
I think it was the “Fat Bee Man” that leaves fire ants untreated near his hives. The reason being that he thinks the fire ants will deal with any SHB larvae that drops to the ground.
Commercial growers are using fire ants as an insecticide here in the south as they eat all sorts of stuff damaging to plants. It’s a bummer if you plant a tree then you have a fire ant mound started. 
First, you should clean your yard neither ants coming back. the same issue had with me but I use an effective building inspection Sydney ants control pest to get rid of them. Their office is located in Sydney anyone can contact them and purchase ant control pest. all the best.