I have an older in-ground pool and under the concrete deck living in the sand/gravel is a colony of flying ants. I have tried for years to eradicate them, but every year they come back. They seem to enter & exit thru the coping thus bringing with them some sand into the pool. Do I need to worry about damage being done to the extent that the deck may cave in because the sand is being removed. Anyone have any ideas about eliminating them? It's bugged me (pun intended) for a lot of years.