Territory disputes? With both species only and community tanks, this can be a potential problem. It can be mitigated by overcrowding, i.e., having so many fish that no single fish can claim a territory. Even if your tank isn’t overcrowded, you can still sometimes ease such disputes if you move things around in the tank frequently (e.g., rocks, caves, decorations).
Though I never posted about it, I ordered some fish back in the summer of last year. In that shipment was six juvenile Julidochromis ornatus. I set up a new 75g tank that would become a Tanganyikan community tank. I put the new ornatus in that tank with plans for them to be an “anchor tenant.” Everything had been going beautifully with them and the other inhabitants (compressiceps, ocellatus, signatus, etc.)….until last night.