Your looking at a 125+. IMO from what i have seen and haveing GT and JD. 90 gallon (same foot print as a 75 but taller) will work for a bit. But being a 4ft tank, once the fish are adult your most likely going to have aggression. But this also depend on the fish. If you get them at the same time you might be able to get away with them in a 90 gallon. You will most like have better luck raiseing them in 125 then in a 90 or 75.