I started that thread a while back on RC. I still see fish from LFS carry flukes. Mainly butterflies, angels, anthias, and wrasses. Tangs rarely gets flukes from my experience. Flukes are hard to see on the fish. They live under the scales and on the gills. Normally with all new fish I freshwater dip the fish for 5 minutes. If flukes falls off (small white opaque sesame sized) then I treat with Prazipro. If nothing falls off Ill just watch for symptoms later in the quarantine tank.
Don't let this happen to you:
When praziquantel reportedly failed to cure fish of flukes in their Atlantic Coral Reef exhibit, the staff at Albuquerque's BioPark Aquarium inadvertently killed about 100 fish - in front of patrons during operating hours
http://www.advancedaquarist.com/blog/public-aquarium-accidentally-kills-100-reef-fish-with-fluke-treatment
Not sure why Prazipro didnt work. It always worked for me. They probably didnt use enough Prazipro.