The African Rift Lake cichlids don't need aquarium salt unless they have an outbreak of ich (there has been alot of debate here at AC over usage of salt--it is just not necessary as a regular additive for your fish. Do a search).
What alot of fishkeepers use to create a similar chemical balance to the Lakes is "Rift Lake Salts", available from several companies. These "salts" are actually just 7-10% salt; the remainder conisists of minerals they "need". ARL cichlids who have been bred in the US/Canada for a few generations have pretty much become conditioned to waters without these "salts," and there are those who do not think them necessary. From my own experience, when I do a partial water change and add the dissolved salts, I see a discernible change in activity in my Peacocks and Brichardi. They act livelier and seem happier; their colors also tend to be more vivid (I've tried going without as an experiment).
I highly recommend SeaChem's Rift Lake Cichlid Salts; they are readily dissolved, highly concentrated, and an excellent price. (Purchased online through PetSmart.) Just my two tater's worth.
RE: substrate: The crushed coral or crushed shells add to the hardness of your water, which is another component of their necessary environment. I mix crushed shells, pea gravel, and sand to provide the males with a great excavating foundation. They love moving the substrate, and it's great to watch these little engineers move shells, small rocks, and sand with their mouths to create a little area to the floor of the tank in which to "dance" with their ladies!!!!! When they get too cocky, I just flatten it and let them start again.
