Holy cow!! 90 gallons! Welllll... I personally would start a saltwater tank full of corals and seahorses and clown fish... But, that's just what I would do with such a large tank.
My lovely bettas are: Dagger, Egg, Salsa, Marble, Augustus, Miles
Puddles, Oz, Nate, Monkey, Picasso, Feng, and Maui