Vieja maculicauda the black belt is a beautiful Central American cichlid. I love this cichlid!!! However, like most Centrals, once they have had a tank by themselves it can be impossible to house other fish with them. You may just have to let him have a tank by himself. And there is nothing wrong with that, I think that they are happier in the long run. After all they are only doing what comes natuarally, protecting their territory. In the wild an intruder can swim away, but in our tank, there is no place for them to go, so there is nothing they can do, except continuing hitting on them until they are dead. Why put your self thru this again?? If you want more fish, it may be time for another tank!
I am currently keeping my black belts with a group of H. nicaraguensis, and they seem to be getting along fine, but they have been together since juviniles, this works best they seem to tolerate each other better when raised together.