Even if they are wild caught I wouldn't go through all the trouble trying to mimic Lake Tanganyika's exact water chemistry. The major issue is TDS, so basically hard water with the necessary electrolytes (most tap water has more than enough) will do the trick. But if you do want to, here's a good guideline...
http://www.cichlid-forum.com/articles/aquarium_salts.php
(table at bottom of page)
http://www.cichlid-forum.com/articles/aquarium_salts.php
(table at bottom of page)
