Let me take you in an entirely different direction: Do a species tank of Neolamprologus brichardi or Pulcher. Put in 6 and they will fill the tank. They breed in multigenerational colonies.
For my money, when I was poking around a 55 Tang tank, I was thinking of putting a big rockplie on the phi spot, and trailing it along the back to a smaller rockpile against theside on the wide end, covering some halved 4" flowerpots. I'd put a sand field on each side (and since I Do do well with plants, I would plant vals behind and among the rocks to the back and put a fringe of Java Fern at the base of the big rockpile, java moss all over the small pile). On the short side substrate I would but a half dozen whelk or tulip shells and on the long side a dozen or more escargot or tulip shells. To this I would add a half dozen pair breeding shellies (Occs or Stapps), and a half dozen colonial Shellies (Multis, Brevis, or Simulus). Were I feeling wealthy, I'd add a trio of Synodontis petricola. Then I would add a half dozen Julies (and start up a 20 long to take the four that didn't pair). I'd go with transcriptus ideally, but my LFS has some beautiful regani "Kigama gold" that I would probably be unable to pass up if I were doiing it right now. I'd probably leave it there, but I would consider for the midwater a Black Calvus (which may or may not work), some Brichardis (again, I would seek better advice first) or, if I were feeling particularly saucy, a half dozen Bosemani or 8 praecox rainbows, or a male and three female marigold swordtails (that can also handle the iron-hard water.)