Only a larger silver aro can handle a breeding pair of festae. But you couldn't house one large enough in a 5x2x2 anyway, so I'd say an aro is out.
G. brasiliensis is a bad idae because they aren't particularly tough and the festae would quickly kill it.
A polleni require different water params, so that is a bad idea too.
Smaller species of cichlids will work and possibly 1 large one. If you had a 6-10 foot length, you could work with a lot more, 5 feet does not allow much room to get away.
In my experience, they don't mind fish that solely stay on the top or on the bottom. So you can do polypterids, maybe clown loaches, and various types of catfish.
For the top, you can use giant danios or an African butterfly fish. If you are really stuck on an aro, you can house one with them as small as 14", but you'd have to sell it a couple months later, or at around 20".