A 210 is a great size tank for breidhori, but even there, you'll need to watch the maculacauda like hawk, and at the first sign of aggression get it out if you expect the breidhori to survive.
Many times an alpha fish will be able to intimidate others into a diseased death.
And this hyper aggressive nature may be reason that black belts are arguably "the" most successful Vieja in Central America. The range spans far north, down into Panama where I live. They seem to eliminate most other Vieja's from whatever waters they inhabit, but also can go from totally fresh water rivers and lagoons, to being seen in brackish estuaries, to the ocean grazing salt water algae temporarily.
Whenever I kept black belts, I ended up giving them their own tanks.