In all honesty right now I think you should just stick with the African Cichlids you have now and no think about any other fish. See how you do with these africans first and do more research. When you feel comfortable with what you have then look into other Africans that you like and then post them on here and we can let you know if they are mixable or not. As for the fish coming with the tank, I agree you need to take them into a local fish shop they dont go together, the Jack Dempsy is going to get to big and they wont mix with the Africans either - if you keep those fish you will have problems.
As for food you need to feed Africans sinking food. No flakes or floating food. If they swallow air from trying to eat floating food your going to have a problem.
As for food you need to feed Africans sinking food. No flakes or floating food. If they swallow air from trying to eat floating food your going to have a problem.