I don't think 59 gallons is suitable for even one oscar. Even though you can keep one in a 55 gallon successfully with very pristine water with a good water change schedule, you need more than that. A 55~59 does not provide a big enough width for an oscar to feel comfortable turning around. I still stand by the 75 gallon minimum for ONE oscar. For two oscars, a green terror, and a proper bala shark school you're looking at a 180+ gallon tank.