Apple snail are no longer and have not been available for several years here
in Missouri. Was told by several stores that they were banned when I
tried to find them.
One thing that comes to mind when I hear Flagtails is the tank.
Glass and Flagtails go together and Acrylic tanks and Flagtails do not. They will fog up your tank from scraping thr acrylic. JMO but thats Y I dont have a Flagtail