I saw the dimensions of your tank in the other thread. If it's indeed 40"x18" then you should be able to keep him in there for life.
I would not keep a FH with parrots for a long period of time. As said the FH will probably kill the parrots. Most FH's will attack/kill most anything you put with it. Catfish/bichir's/etc.. At least in that small of a tank. I wouldn't try putting anything with it unless you had a tank 100g+.