While i dont actively recomend keeping exodons with other fish i have to say that i dont follow my own advise there. I have found that it is possible to keep exodons with equally aggressive fish or those that are 100% nocturnal without any major problems, i keep my school of 9 exodons with 2 Leporinus fasciatus (truely nasty evil fish) a couple of large Hoplosternum thoratacum (their heavy armoured scutes protect them) and a Heteropneustes fossilis (strictly nocturnal and pretty aggressive as well as having venomous spines) all of which can look after themselves against the exodons.
However with the bichir having large soft fins and being fairly placid and slow moving i think there is too much risk of damage from the exodons nipping to risk housing them together, but having exodons doesnt always mean a complete species tank.
PLEASE NOTE WHAT WORKS FOR ONE FISH KEEPER MAY NOT WORK FOR EVERYONE, ALL FISH ARE MIXED AT YOUR OWN RISK.