I have been led to believe that a silver aro is your only choice in Florida. Silver aros grow very quickly 1 to 1.5" per month on average. Once they get to 24" there growth does slow.
So within 18 months or so you will need to have a tank large enough for a 2 foot fish. Eventually the aro will grow to well over 30". So recommended tank would be a 180g 6x2x2 foot tank then upgrading to a 300g 8x2.5x2 foot after a few years.
Learn as much as possible before getting an arowana. This is not a beginner fish.