I'll have to go with Ulrichsd on this one. Demasoni are some of my favorite Mbunas, but they have very high conspecific aggression. I have 11 of them in a tank that's 6'4" long, id, with Malawi butterflies, redfin borleyis, acei, and yellow lab, so there are plenty of other fish to entertain them, and plenty of hiding places and caves, so I don't have an aggression problem anymore. I used to have 7 Demasoni and 5 yellow labs in a 55g. The dominant demasoni eventually killed 3 other male demasoni, even though I routinely rearranged the decor. They won't be aggressive toward the bumblebee, but unless you have a large enough group, and enough hiding places, they will be with each other.