Agreed. 55 gallons should give you ample space for a Mbuna setup. As said above, they need large amounts of rock to establish territory. They do prefer a higher pH, but through immense amounts of aquarium breeding, they have become adaptable to a wide range of pH. Anything about 7.0 should work fine for them. The rock will also help raise the hardness of the water, which is actually more important for the health of the fish than the pH. A lot of people use marine substrates to accomplish this.
I had an African Cichlid setup in my 55 gallon for a short time stocked with P. Demasoni and L. Caeruleus. The deep blues and bright yellows made for a stunning contrast and the aquarium got a lot of attention.
The most important thing when you're considering a fish is doing the research to determine it is the fish for you in terms of behavior, aesthetics and water conditions. Let us know what you find.
