In a 90 gallon:
12" Jag, add 2 6" oscars=harrassed and beat up oscars
12" Jag, add 7 giant danios=nervous and scared danios that don't get eaten because they are too fast for the jag but they commit suicide 1 by 1 by jumping out of the smallest of openings in the lid.
12" jag, add a 4" male convict=lived pretty much in peace for 2 months then the jag decided "I'm gonna eat you now-you are starting to annoy me."
In a 100 gallon long (6'x18"X18"):
14" Jag + 10" Red Devil + 10" High Fin Pangasius Catfish + 8" Gibbiceps Pleco + 2 Spotted Raphael Cats =a very entertaining mix after 2 months-the jag and devil fight and joust at times and at other times they look like they are best friends-weird! They both take shots at the Pangasius. The additon of the RD has made the Jag a less finicky eater (competition now). Many have said it is only a matter of time-someone is gonna get hurt real bad. Pleco is pretty much ignored as are the rapheals. Big monster tank needed in the future, I know.