niger triggerfish

Hi!! I've got a 100 Gal FOWLR tank with 2 Niger Triggerfish, they're 3.5". i got them a month ago. I'm planing to get a new 180 Gal or more in about a year for them. I know the can get 1' or more commonly 8" -10". A friend of mine had some triggers many years. But, for now, i would love to add...