Natives are great fish as a whole, and often over looked by Australian fish keepers.
I have a Mangrove Jack at 45cm, that has to also be kept solo. He lasted with tankmates until he hit around 25cm. Now he attacks everything, including me.
I also have 2x Archer fish in another tank, both are 20cm +
Archers are one of my all time favourite fish; they look cool, can shoot water, are hardy (easy to care for), cheap and are model aquarium citizens. Can't really ask for much more out of a fish!
My Jack is in a 5x2x2 which is getting a bit small, he will be moved to my 8x3 when we move house early in the new year. I'm considering maintaining his new home as a marine environment. As most large mangrove jacks are found on off shore reefs. Added salt may enhance his growth rate and get all I can out of him.
MJ's are one of the most amazing fish I have ever kept (and I have kept just about everything). The only downside could be said that most will eventually need their own tank, but to me that is half the attraction. Dovii, Jag's and other Cichlasoma seem like skirts after keeping an angry Jack!