This is a bunch of my non-mbuna cichlids. It is a lucky shot because very rarely you can see all these Nimbochromis species located at the same spot. You can see a male Nimbochromis venustus with two of its females (left part), a male Copadichromis azureus (center) the female Nimbochromis polystigma (center, top), the male Nimbochromis livingstoni and the tail of the female Nimbochromis livingstoni. Non-mbuna cichlids of Lake Malawi are collectively called Haplochromines (haps for short). These fish are larger than the mbuna, less vividly colored (though this doesn't mean colorless) and form the most diverse groups of Malawian cichlids.
Half of them are omnivorous, one quarter are predators and the other quarter are herbivore or filter feeder. They have an interesting and varying behavior and are found in almost every habitat in the Lake Malawi. In the aquarium they are generally less aggressive than the mbuna provided all species kept are of the same size and temperament. The aggression is limited to spawning time and this is mainly due to the fact that these species, in the natural habitat, defend huge territories which they can't possibly have in the limited space of any tank. In a tank like this one, each species will find its own site and aggression will be kept to a minimum. Males will chase the females around but aggression between different species is kept well under control even between species very closely related (like the Nimbochromis species in this photo). Their movement in the tank is slower (compared to the nervous and aggressive movement of mbunas) and far more majestic than the latter. This is partly due to their bigger size which gives a different impression, since everything they do seems "bigger". Their bigger size will limit the number of individuals in any tank and this is a good reason why most hobbyists prefer the mbuna species.
Another problem is that, once your fish grow to their adulthood then you can't introduce small fish in your tank since it will be regarded as food and will be treated like food. This of course adds to the cost of getting new fishes and needs your attention in removing your carrying females in time. Practically, no fry will survive in such a tank, no matter how many hiding places you have (another difference to the mbuna tank). Spawning will take place easily if the water chemistry is right and this is not difficult to be done. Another difference is that you can expect really big broods since even 100 fry is not rare for grown up fishes. Sand is the gravel of choice for the Haplochromines and can't be substituted by coral sand or crashed oysters.
These species like to play with the sand, move it around, create their spawning sites, clean their gills with is, scratch on it. This is my personal experience but it is highly recommended. Transferring, washing and cleaning it is a difficult and time consuming task but the result justify it. It took me 200 kilos of sand to cover the bottom sufficiently and another 200 kilos of rock to create a barely sufficient rockscape. Addition of Sodium bicarbonate (baking soda) will buffer the water and bring the pH at around 8.0 (and, most important, keep it there). Addition of Aquarium salt is up to you. I use it but I know it wouldn't make much of a difference if I didn't. Initially I also used the so called "water hardness raising" stuff but after a month or so I stopped it. My fish thrive even without it (if they even noticed it's absence). Feed once per day for six days (I don't feed them on Sundays). Still they look like overfed to me. I am thinking of taking one more day without feeding.
Though not herbivores they will definitely take some bites on your plants. This is natural for species like Protomelas but even classic predators will eat the soft edges of your plants. They say that no cichlid will eat Vallisneria gigantea but I can tell you from my own experience that it has become a regular meal for all Protomelas but it also a snack for Nimbochromis species which also like Corymbosa top leaves. Just compare the Vallisneria in the initial tank photo to the last one, and take into account that this plant has produced 10 more runners after the first photo. Vallisneria consumption reaches its peaks during non feeding days, so it looks more like changing their diet rather than fasting them. Seven months later, the whole plant is consumed.
I have included some photos and close ups of these species in this site - enjoy them.