Uh, I assume the screeners here will confirm that there's no TSA policy barring tropical fish from flights. How can it be any different from a dog? Or a manatee (see previous post).
This is a classic example of a supervisor that should be publically fired, humiliated by name in several newspapers, and barred from government-related work for life. In a way, it's too bad she didn't kill the fish--because then she might be able to sue the guy for emotional distress. I hate frivolous lawsuits, but if I were on the jury, I'd find in the student's favor.
Setting a few examples like that would be a great deterrent to this sort of stupidity.
And TSA needs an effective escalation policy that goes beyond the local supervisors for dealing with screeners that try to bar non-prohibited items carried by pax.