Has anyone had success with keeping multiple cichlid pairs of the same or different species together in the same tank?
The tetras are a really neat ideaBasically what Duane said.
You can get away with more pairs with dwarf cichlids or fish that live in close proximity in the wild (Archocentrus multispinossa). A lot of people have success with groups of Thorichthys, but the tank needs a ton of cover which may detract from the look of the tank if its a display.
In a six foot tank, you are fine with most of the medium sized pairs. There is a delicate balance between the two pairs. One tip is to include a school of medium sized tetras so that the fry get eaten as they venture further away from the parents. If you don't have a way to prevent fry from wandering, the parents try to guard a larger territory which may cause the delicate balance to fail. Several species ofTanganyikan cichlids do well with multiple pairs, they tend to hold tight to their territory. Of course there are exceptions.
I don't keep large fish, so I can't comment on how they do in multiples. I would think poorly, as their territory requirements easily span the whole tank.