Noooo. Demosani are one of the most aggressive. You don't want to in a smaller aquarium(under 100g) keep more then one male Demasoni. And I proved it true after owning one after hearing that and not knowing if this was true or not. That little guy will murder anything that looks similar to him. Only thing that calmed him some was when they outgrew him and the dominant male in my tank is extremely aggressive and has put him in his place. Also the african featherfin cat has had a calming effect on my Mbuna tank.If you chose to go with Demasoni as one of the species, go for 2 males and 8-10 females, smaller size, and a bit less aggressive, so higher numbers will help them stand against the other species. My plan was Demasoni (Blue, black barred) 2M 8F, Psuedotropheus Acei 1M 3F and Red Zebra 1M 5F. I found almost all of the info I needed here:
What is an easy, colorful stocking list for a Mbuna tank?
Hope some of that helps! Keep us posted!
Don't be discouraged Smit! You can order your whole stock online for decent prices if you want to move forward with your Mbuna tank. and it's not a "possibility of aggression" it is guaranteed aggression with them but really once you have started and done your research and stocked and settled them in the aggression becomes manageable and the amazing behaviors of these fish by far outweigh the aggression.