Thats a huge tank but they are just too many options for us to help you with it first you would have to decide what types of cichlids to do. At that size a malawi predator tank might be nice, or a frontosa harem. But there are literaly hundreds of cichlids you could try. But it is best to stay with one group. such as malawi mbuna, or peacocks, or haps. Then in lake tangyika there are several more options again. The tank would work best if you only had fish from one of these groups due to habitat, diet, and agresion, though you can mix carefully if you are determined. So do a bit more research and see what your intrested in we can help you from there
Plants are very limited, the cichlids tend to dig them up, or eat them but anubias' and java fern tend to do well in most tanks
Edit- I was thinking this for the 6 footer ---not really sure what your asking