Amdro Fire Ant Bait is labeled for Argentine ants. You would sprinkle 2-5 level tablespoons of Amdro Fire Ant Bait around the mound, for normal sized mounds. . Be sure not to disturb the mound. Please see the product Label for specific rates.
You should not need to change the water if Amdro Fire Ant Bait gets into the pool. Once wet the product breaks down and only contains a small amount of active ingredient to kill insects.