Welcome to the forum! As for bullfrogs, I've heard that a single adult requires as much as a 75-100 gallon tank. Now, I could be wrong, and I probably am, but why not get an African bullfrog instead? They're bigger, have a more "badass" look to them, and they require less space than American bullfrogs. If you want a more traditional/froggy-looking frog that's easier to care for, you could also start out with a leopard frog. Those are my suggestions, but naturally you should get whatever you want as long as you can provide for it. I'll shut up now, and welcome to the forum!