Hey, Robert!
I'd suggest fish - like the triggers - where you can impart some useful information, or bust a myth, such as "all damsels are the spawn of Satan", "Which angelfish are the most reef-safe", or "All parrotfish eat live coral and poop beaches". Other great topics might include fish that are _very_ tempting, such as mandarins, butterflies or Achilles tangs, and what needs to happen in order for those fish to be cared for appropriately.
Another great group to feature would be the increasing number of fish that are being captive-bred.
Just a few off the top . . .
~Bruce (Who has a blue-jaw triggerfish and a recalcitrant Quoy's parrotfish, and wants a pair of green mandarins and an Achilles tang . . . (9_9)