come on guys, i know aiptasia is annoying, but that doesnt really work out.
ok assuming you have a completely clean setup, so what's next?
are you going to boil and sun dry the corals you buy?
are you going to boil and sun dry the fishes you buy?
if not, the rocks that come with the coral you buy may be infested with aiptasia, the water from LFS might have floating aiptasia tissue which can grow into aiptasia.
you will get aiptasia in your tank sooner or later, so get used to it and get it under control by means of using natural predator or chemicals