It depends on the size of the tank. I keep Julidochromis transcriptus with 'Lamprologus' stappersii in a 29 gallon tank. The Julies can be aggressive, but I've never seen them kill another fish, they just chase the shellies away from their nesting area. I don't have a pair of shellies, so there is no spawning. Don't know if that would change the aggression level or behavior.
Here's a transcriptus letting the stappersii know who's boss.
The Julies have raised fry successfully with the stappersii in the tank.
I wouldn't keep them in a tank smaller than this and larger would be better.