I would ever go with a large group of Exodons , a few Gulper Catfish , or maybe a large goup of all diffrent types of Bichir and Rope Fish .
But depending on the size of the 80Gal and/ or if you plan to upgrade you could get a few small Cichlids or other type of fish to grow out in the tank and then buy a larger tank for them later on when they get too big for the tank .
I would not go with a school of Red bellied piranha tho ! They would get to big to fast for that tank and would think about getting a larger tank first to have a nice group of Red bellied piranha , IMO something like a 5x2x2Foot tank to have a group of 8 or so .
