whats in the 75 right now? because it would have to be pretty big to make a 6" aro a meal. im not attacking you man, im just giving you proper advise. they are a very active fish and need a large footprint tank so they can swim back and forth while still being able to venture front to back as well. not sure about afro's, but all aros are a carnivoris fish, they will eat anything, pellets, fish, anything edible. and they do jump, so you might want to cover every opening.
sorry if we sounding like we were jumping on your case, but proper care for a fish is a priority and not something that is taken lightly. just remember that.