If I could afford the electric bill for the pump for a tank this size, it would have to be filled with Angelfish and huge schools of Tetras if it were Freshwater. There's nothing like watching a wave of Tetras swim over a school of Angels or Discus.
If it were saltwater, a living reef with schools of assorted cardinals, anthias, tangs and surgeons and maybe an angelfish or 2, some butterflies, can't forget some heniochus, oooh and some wrasses, damsels, basslets and maybe some cat sharks, oooh, I forgot, also a clown trigger and some Niger triggers, CLOWNFISH!!! How could I forget some clownfish???!!!