When it comes to keeping shell dwelling cichlids, they're usually kept in single-species tanks to avoid them becoming someone else's meal. However, there are some peaceful fish that can coexist with them.
For instance, Cyprichromis leptosoma and Paracyprichromis nigripinnis are great options. These schooling fish grow to about 4 inches and tend to get eaten by larger fish in the lake. They're very peaceful and have small mouths, which makes them a good match for your tank. The males display some colour, but the females are quite plain. To keep them happy, keep them in groups of 10 or more and make sure they're well-fed. This will encourage them to breed.
Another species that might interest you is Lamprichthys tanganicanus. It's a relatively small fish, also growing to about 4 inches, and can be kept in groups.
In terms of water parameters, Tanganyikan tanks typically have a GH of around 400ppm and a pH of 8.4+. However, locally bred fish can thrive in water with a GH of 300ppm and a pH of 8.0.
Given the high pH levels, it's essential to cycle your tank before introducing any fish. This will prevent ammonia poisoning and ensure a healthy environment for your fish. If you have an existing tank, you can use some of the filter material to speed up the cycling process. Otherwise, a fishless cycle should take around 4-6 weeks.
When it comes to feeding your fish, they tend to prefer marine-based foods like fish and prawn. Baby brine shrimp is an excellent option, but it's crucial to provide a varied diet that includes foods like mosquito larvae, daphnia, Nexarios, microworms, grindal worms, and white worms. While they may not eat a lot of dry floating foods, including some in their diet will help ensure they get a balanced meal.
For more information on culturing foods for your fish, I recommend checking out this link:
http://www.fishforums.net/threads/back- ... sh.448304/. It's primarily focused on breeding fish, but the information can also be applied to culturing foods for adult fish with small mouths. I'd recommend starting to culture live foods at least a month before introducing your fish to the tank.