This is from the owner of Live Fish Direct. Some of these suggestions surprise me, but I'm no expert.
African Cichlids
1. Stocking Levels VS How big is the tank in gallons
a. These notes explain how many fish can fit into the tank. For example the first line is explaining that in a 30 gallon tank 8 would be lightly stocked, 12 would be average stocked, and 15 would be densely stocked.
i. 30 gallon = 8, 12, 15
ii. 50 gallon = 15, 20, 25
iii. 75 gallon = 25, 30, 35
iv. 90 gallon = 30, 35, 40
v. 125 gallon = 35 , 45, 50
vi. 150 gallon = 40, 50, 60
vii. 250 gallon = 60, 80, 100
viii. 500 gallon = 100, 130, 175
b. Stocking levels will determine a balance between water quality and aggression
i. The lighter you stock the less you will have to change the water but the more the fish can damage each other due to aggression
ii. The heavier you stock the tank the less likely your fish are to damage each other due to aggression. They will still chase each other around all day but this method of dense stocking I have deemed “chaos theory” and it works.
3. Compatibility
a. Mbuna and Victorian Cichlids are more colorful at a small size. They are the heartiest, cheapest, and most colorful. They are also the most aggressive, but can be kept with peacocks and haps with no problems as long as they are introduced with a size disadvantage to the less aggressive species. A really nice look for a cichlid tank is to have a bunch of smaller mbuna and Victorian cichlids running around with some bigger showier male peacocks and haps.
b. Cichlids are more compatible if they are all added when young and are raised together. If you have a larger tank I usually recommend going in 6 packs of small fish to reduce costs and increase the chance of getting a nice cherry male of the group you will be proud of because you raised them yourself. By starting all the fish off young and raising them together I have seen fish tanks that would be considered completely incompatible but they have no problems. This is just like raising a puppy with a kitten.
c. Cichlids get along better in larger sizes if there are smaller more aggressive fish around to distract them from picking on each other. You can keep a batch of aggressive male haps and peacocks from hurting each other by adding some small colorful but aggressive mbuna cichlids that are hardy. We call these “dither” cichlids as they help create the “chaos” mentioned above.
d. Males that look just like each other will quarrel the most. This will bring out their best color but may be stressful to watch as they go at it. As long as you use the tricks mentioned earlier such as stocking densely and using dither fish similar males should not do any real damage to each other. However the aspect of Male dominance must be accepting in Cichlid tanks. Fighting is just what they do!
4. Sex
a. Mbuna cichlids in the Green color code category have colorful males and females.
i. Female mbuna can be mixed with more mild species. Larger female mbuna can help add color to a tank and will technically keep the peace.
b. For the best color aim for an all male tank. There is nothing wrong with going for an all male tank if you have no desire to breed fish.
c. If you do want to breed fish you want at least two females to one male. For the record there is nothing wrong with 6 females to 1 male if you really want to breed fish that is how it is done.