The only potential aggression problem might be Metrialima emmiltos. This fish is often called the "Red Top Zebra" and can be quite aggressive to conspecifics, and due to similarity in looks the chailosi and afra might be picked on. Now, I have never kept this species so hopefully someone can comment from their own experience.
I will also add that in a 90gallon tank, if you have enough rockwork and sight breaks it probably won't be a problem.
Lastly, be careful of the size mbuna you get and the size venustus you get. If the mbuna are small enough the venustus might have a snack. Basically if the mbuna are small enough to fit in its mouth then you could have a problem. Venustus are known to hunt small mbuna. As long as your original stock of mbuna are large enough the venustus can be quite helpful with fry control. Mbuna can be quite prolific breeders in a healthy tank with good M:F ratios. It is fun to watch, but before you know it you have way more fish than you started with. Most of the fry in my tank get eaten, but two are now large enough to to be safe. I have probably 20+ fry in the tank at a time, but the number dwindles until a new female spits her fry.
By the way, you better post pics when you get these new fish!!! Love to see people's tanks.
