Shell dwelling cichlids are normally kept in colonies in a single species tank so they don't get eaten by bigger fish. There are a few smallish peaceful fish that you can keep with them.
Cyprichromis leptosoma and Paracyprichromis nigripinnis grow to about 4 inches and are a schooling fish that get eaten by bigger fish in the lake. They have small mouths and are very peaceful. The males have colour but the females are plain. Keep them in groups of 10 or more and feed them well, and they breed readily.
Lamprichthys tanganicanus is another smallish species (grows to about 4 inches) that would be fine. Get a group of them as well.
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Tanganyikan tanks have a GH (general hardness) around 400ppm and a pH around 8.4+. Locally bred fish will be fine in water with a GH around 300ppm and a pH around 8.0.
Because of the high pH, you need to cycle the tank before adding any fish otherwise the fish will die from ammonia poisoning. If you have another tank running, you can use some of the filter material from the established tank to help speed up the cycling process. Otherwise do a fishless cycle and in 4-6 weeks, you should be able to add some fish.
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The fish I have listed, and the shell dwellers you want, do not normally eat a lot of dry floating foods and do best on marine based foods like fish and prawn. Baby brineshrimp is an ideal food for them, but they need a variety of different foods like mozzie larvae, daphnia, rotifers, microworms, grindal worms and white worms. Dry food should also be included in their diet so they get a more balanced diet.
The following link has information about culturing foods for baby fish but the information can also be used to culture foods for adult fishes with small mouths, (like the ones I have listed). You should start culturing live foods at least a month before you get the fish.
http://www.fishforums.net/threads/back-to-basics-when-breeding-fish.448304/
