When i have tried to keep them by them selves they were very shy and would hide most of the time. Mine were also alot more skittish and stressed when they were alone. I contribute that to them getting sick very often with fungus and fin/tail rot and eventually dieing. When i kept a group of 3 and then 4 they were outgoing and lived for years disease free until i traded them off. I also witnessed my ace falctuses schooled well with hujeta characins. And i would think they would make a good companion if more cuda's were not availiable.