Your aquascaping looks great, and the size of the tank is everyone's envy. However, I am no fan for an all Malawian cichlid tank, and won't jump into the bangwagon to praise your fish. Even though Lake Malawi has over 1000 distinct species, they are very similar in body shape, markings, color and behavior. So despite having 18 different species and 50 to 60 fish in your tank, they are a crowd of similar looking fish. Eventually, your haps will all color up, your Fosso will reach big size, but they will still be a bunch of bluish fish. Size matters. With a huge 500 gal tank, it's a waste not to house a few monster fish from outside one lake to provide variation in color, body shape and behavior. I personally like to mix in CAs with Africans as they have similar water requirements.