Otherwise it's wide open depending on what you like. I'd strive to keep small groups of any species you choose so you get both males and females (5-6 fish) and try to choose species that look different from one another in color and/or body styles. For example, if you get a blue mbuna with stripes, don't get another species that is also blue with stripes. If you get one type of zebra, don't get a second type of zebra, even if it's a different color. This is to keep interspecies aggression down and lessen the chances of hybridization. The easiest rule of thumb would be to pick only one species from any genus (though the Psuedotropheus genus might be an exception to this since there are a wider variety of species in this genus compared to the remainder).
I actually had a question regarding this - is there a hard fast rule about keeping mbuna of the same genus? I was wanting to get a few different types of Metriaclima but I am scared of hybrids. The ones I want are of different color (therefore following the different pattern/color rule) but I just don't want to have to deal with hybrid later on. Will this affect breeding for the cichlids ? (i.e. dominant male won't let other males breed with their species - even if the dominant male wants nothing to do with the females) The mbuna are going into a 90 gallon so they should have lots of room. Has anyone had success keeping multiple species of mbuna this way without hybridization? Just want opinions before I invest in some stock. Cheers!
The fast rule would be, only one species from a given genus in a tank (but isn't foolproof). With respect to mixing zebra species for example, even if you get blue ones, orange ones, and red-top/blue-body ones, they all have a similar body style aside from the specific color and are more likely to hybridize. A better route would be something like blue M. cyaneorhabdos, orange M. estherae (orange zebra), and red-topped L. trewavasae.
A dominant male won't protect species of his own even if he doesn't want to breed. A male who has species of his own kind, will tend to attempt to breed with them before others most often. A male without any species of his own in the tank is the most likely to breed with others.
However, from a number of studies I have read, naturally it's the female of a species that determines the choice of a suitable mate for spawning. She'll have certain keys she's looking for, such as coloration or pattern, fin style, body shape, etc.
