funk, funny you say that, freshwater cudas was what I was going to suggest.
A few acestorhynchus would be fine in an 80 gal, as long as it's wide enough. They are fast, flighty fish. They don't grow huge, but need more room than your average fish that's 6/12 inches.
I've owned wolffish and acestros, take it from me, acestros are WAY more fun than a malabaricus. One of the most underrated fish out there - acestrorhynchus.