The Bloody Parrots without tails have been cut, this is known, and equated to clipping the ears of a Doberman to make them stand up (I don't agree with either practice). As for the Angelfish, I suspect the same. And I would first make sure the shop knows this, and let them understand that continuing to sell such fish will damage their reputation. They may not be aware of how the fish are made. Should they continue to sell those fish after being informed, then I would no longer patronize the store, and make sure that their reputation gets damaged.
There are two kinds of error: blind credulity and piecemeal criticism. Sound skepticism is the necessary condition for good discernment; but piecemeal criticism is an error. - Egyptian proverb