I dont agree that 80 gal is enough for a jag, the following line is taken from a website I've looked at:
"For a single specimen 125g tank should be used to comfortably house it and a breeding pair should have 180g or more and must absolutely be kept alone. A single full-grown jag should be kept in a 180g if tank mates are present."
Also for an oscar you would need a 75 gal tank but that would be with 1 oscar only and no other tank mates, plus LOTS of filtration
Andy