bare minimum i would say is a standard 75 gallon. But a bigger tank if you can afford it is always better and the fish would be more happy.
+1 as well.....I have "accidently" breed these bad boys years ago. I kept one of the babies for me and he lives solo in a 75g. Might move him to a 125g if optional. But overall, 75g 48inch by 18 foot print should be fine for life.