Lol I had a huge aquaponic dwc raft setup outdoors, (35,000 gal to be exact) and every now and again I would get fire ants building nests in 2" net cups...they would build trails from one whole to another on top of 2ft of water until 12 or more were connected. At first I was alarmed and thought just as you, "this can not be good", but after years of being used to seeing this I quickly noticed a huge difference In the health and vigorous growth from these plants that were chosen by the ants! So I'd watch and observe before dousing your plant with. Neem.
On the technical side I still to this day am not sure what they were doing, but at the very least puting holes near the roots allowing for more oxygen. Also ants carry bacteria that they make and cultivate in their burrows, so maybe the plant is being protected by the bacteria, much like worm casting bacteria?
